Electoral Vulnerability and Legislative Responsiveness

Electoral Vulnerability and Legislative Responsiveness

Abstract
This paper focuses on the relationship between legislators’ electoral vulnerability and their

legislative behavior. I develop an alternative measure of electoral vulnerability: estimation based
on several indicating variables including campaign expenditures, previous electoral margin, and
district partisan support. Using this measure, I examine legislative responsiveness in the House
during the 109th and 110th congresses, and find that electoral vulnerability is positively related to
responsiveness. More vulnerable members better reflect constituency preferences in their
legislative activities. Additionally, vulnerability plays an important role in individual roll call
decisions. Vulnerable members are more likely to support bills when there is a bandwagon to
jump on and shy away from bills that take place close to election time. This paper sheds light on
our understanding of electoral vulnerability, finds evidence supporting the marginality thesis,
and explores conditions under which vulnerability influences legislative votes.

By Ruoxi Li
Department of Political Science
University of Wisconsin-Madison

April 2013

Paper prepared for: American Politics Workshop
University of Wisconsin-Madison

Introduction
The relationship between electoral vulnerability and legislative behavior has important

normative implications. Whether or not electoral vulnerability has direct influence on legislative
outcomes is one of the fundamental questions of democratic representation. This topic first drew
extensive scholarly attention in the 50's (e.g. Macrae 1952, Shannon 1968,
Sullivan and Uslaner 1978, Cohen and Brunk 1983), and has experienced a revival during the
past decade (e.g. Gulati 2004 , Griffin 2006a, Gay 2007). No consensus in on this question has
been reached. The best that can be said about the effect of electoral vulnerability on legislative
outcome is that the results are mixed.

This paper adds to this literature by first arguing for an alternative conceptualization and
measurement of electoral vulnerability, then examining the effect of electoral vulnerability on
legislative responsiveness, and also looking for conditions under which electoral vulnerability
has a substantial effect on representatives' roll call voting decisions. First, I argue that electoral
vulnerability can not be fully captured by the single variable of electoral margin. Electoral
vulnerability is subjective and dynamic; I measure it as a latent variable indicated by several
relevant factors including incumbent and challenger campaign spending, district partisan vote,
seniority, and previous electoral margin. Second, I argue that electoral vulnerability does not
have the same, universal impact on legislative decisions. Electoral vulnerability is likely to have
a stronger effect on some bills and a weaker or no effect on others. The focus of previous
scholarly debate is whether or not electoral vulnerability has an effect on legislative decisions;
this is only a first step that needs to be supplemented by a more nuanced understanding of the

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effect of electoral vulnerability. I hypothesize that the effect of electoral vulnerability is related
to policy area, general level of bill support, and timing of the bill.

The empirical analysis consists of three steps. The first step is to derive a new measure of
electoral vulnerability. I use factor analysis to estimate an electoral vulnerability indicator for
each House member of the 109th and 110th Congress. I find that most legislators are reasonably
secure, with a few that are highly secure or highly vulnerable. The second step is to use the
vulnerability indicator as an independent variable to explain legislative responsiveness. I find
that vulnerable legislators follow district partisanship more closely with their own political
ideology. Additionally, electoral vulnerability has a significant impact on about 12% of House
roll call votes of the 110th congress. The third step is to understand conditions under which
electoral vulnerability has a substantive impact on legislative votes. In this step I let the
coefficients of the vulnerability factor be the dependent variable, and find that level of bill
support is positively related to the effect of vulnerability on legislative decisions.

The findings suggest that it is too early to conclude that electoral vulnerably does not matter
(e.g. Kuklinski 1977 , Gay 2007) More effort is needed to better measure electoral vulnerability
and to understand the conditions under which electoral vulnerability influences legislative voting
decisions.
Theoretical Considerations

Literature review: an ongoing debate
A repeating pattern in the marginality literature is the inconsistency between an intuitively
straight-forward theory and the lack of supporting empirical evidence. The original marginality
theory uses electoral margin to measure electoral vulnerability. Its proponents make the

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argument that electoral margin is positively related to party loyalty and negatively related to
constituency representation. Electoral margin, they hypothesize, “…[sensitizes the legislator] to
the wishes of constituents in his quest for support at the next election (MacRae 1952: 1046)”.
Early studies on the marginality theory find mixed results. On the one hand, Froman (1965) finds
support for the marginality theory using congressional data from the 1960's. Bartlett (1979) finds
that electoral margin is positively related to legislators' voting decisions on congressional pay
raises. Kuklinski (1977) finds a limited, conditional relationship between marginality and policy
responsiveness using state-level data from the late 1960's and the early 1970's. On the other
hand, Cohen and Brunk (1983) find no relationship between marginality and party loyalty score
using congressional data from the 1950's through the 1980's. Deckard (1976) similarly finds no
relationship between electoral margin and party loyalty after controlling for district level
demographics.

In spite of the mixed empirical results, the concept of the marginality theory continues to play
a role in explaining congressional voting behavior. Electoral margin is often included as a
control variable explaining legislative voting decisions (e.g. Bartels 1994). The theory has
traction because it makes intuitive sense and is supported by formal theoretical analysis.
Anecdotal evidence too often points to the importance of electoral consideration in legislators'
voting decisions. Controversial legislations are perceived to be situations where vulnerable
legislators are in the unenviable position of having to choose between responsiveness and
responsibility. News reports frequently quote legislators who cite electoral vulnerability as their
main reason for refusing to support controversial bills. Campbell (1981) makes a formal
theoretical argument showing that as long as voting decisions are perceived to be linked to

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electoral results,1 legislators will make voting decisions in accordance with their electoral
margins.

Thus, even though the marginality thesis has failed to gain sufficient empirical support,
scholars are reluctant to conclude that electoral marginality does not matter in electoral voting
decisions. A recent round of research brings the attention back to the marginality theory. The
findings, again, are mixed. Griffin (2006) finds positive relationship between electoral
competitiveness and incumbents' legislative responsiveness using congressional data from the
70's to the 2000's. Gay (2007) finds no relationship between district competitiveness and policy
responsiveness in the context of majority-minority districts in the state legislature. Gulati (2004)
even finds a negative relationship, that is, legislators from competitive districts are in fact less
responsive to public opinion and more partisan compared to legislators from noncompetitive
districts. The disagreement in regard to the marginality theory continues on with more advanced
data and research methods. However, the problem with the literature may be less about data and
methods but more about the conceptualization and measurement of electoral vulnerability. After
all, electoral margin, albeit important, is only one way to conceptualize and measure electoral
vulnerability.

Electoral vulnerability: subjective and dynamic
The core concept of the marginality theory is that electoral vulnerability matters in legislative
voting decisions; those who are electorally vulnerable are more sensitive to voter preferences and
more resistant to party pressure. A fundamental problem in the marginality literature is that
electoral vulnerability is simply considered as legislators' vote share from the previous election,

1Empirical research suggests that voting decisions are indeed directly related to election results, see (Bovitz and
Carson 2006)

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that electoral vulnerability equals electoral marginality. But it is not necessarily the case.
“Electoral statistics cannot capture the uncertainty members feel about their renomination and
reelection. (Fenno (Fenno 1978):36)” To conceptualize electoral vulnerability as marginality
overlooks two important aspects of electoral vulnerability. The first is that electoral vulnerability
is incumbents' subjective perception; the second is that there are possible discrepancies between
vote margins from previous elections and electoral vulnerability in the current election cycle.

To better measure electoral vulnerability, it is necessary to take into consideration its
subjective and dynamic nature. As Fiorina (1974) points out, electoral vulnerability is a
perception in the mindset of legislators. If electoral vulnerability affects legislative voting
decisions, it is the subjective perception of vulnerability that matters. Few in the literature have
attempted to measure the subjective perception of vulnerability. Some may argue that survey
questions asking incumbent legislators about their perceived level of electoral vulnerability is a
direct measure. The problem with this type of data is that they are difficult to obtain. Even if they
are available for research, survey answers may not be a good indicator of electoral vulnerability
because they can simply be “cheap talk”. Cohen (1984) shows that legislators across the board
stated feeling electorally insecure regardless of their actual winning margin. These survey
answers turned out to be uniform and lacked variance because they were costless and therefore
unreliable signals. Legislators could easily overstate or understate their perceived level of
electoral vulnerability without additional cost. Therefore, survey data, though seemingly straight-
forward, are not the best indicator of electoral vulnerability.

I argue that an incumbent's campaign expenditure in the current election cycle is a useful
indicator of the subjective perception of electoral vulnerability. The reasons are two-fold. First,

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campaign expenditures are controlled by the incumbents and therefore subjective signals. When
legislators perceive themselves as vulnerable, they are likely to raise and spend more money in
election campaigns. Second, campaign expenditure is costly; it takes considerable effort to raise
money and strategic consideration to spend money. Thus, large amount of incumbent campaign
expenditure tends to reflect a sincere feeling of electoral vulnerability; it is too costly to be
merely cheap talk.

Another feature of electoral vulnerability is its dynamics. While many factors relating to
electoral vulnerability, such as district partisanship, remain relatively constant from one election
to the next, some important ones change across elections. For example, studies have shown that
the emergence of strong challengers significantly affects election results and renders incumbents
more vulnerable to losing (e.g. Jacobson and Kernell 1981, Jacobson 1990, Lublin 1994). Such
dynamics can not be captured by electoral margin from the previous election cycle. While some
scholarly work attempts to account for the dynamics of electoral vulnerability by including
changes in electoral margin in addition to the absolute value of electoral margin (e.g.
Cohen and Brunk 1983), these measures still fail to capture the dynamics of electoral
vulnerability in the current election.

Compared to electoral margin, which only indicates past electoral vulnerability, campaign
expenditures towards an upcoming election indicate the current level of electoral vulnerability.
In addition to incumbent spending, challenger spending is also an important indicator that
captures the dynamics of incumbent's electoral vulnerability. It is both a reflection of
incumbents' inherent electoral vulnerability and a contributing factor that increases incumbents'
vulnerability. On the one hand, strong challengers emerge and spend significant amount of

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money in election campaigns when the incumbent is weak; on the other hand, the emergence of
and spending by strong challengers increases incumbents' vulnerability and decreases their
chances of winning. Thus, incumbent campaign spending and challenger spending are important
indicators that capture incumbents' electoral vulnerability.

Some recent scholarly work has recognizes the limitation of electoral margin and uses
alternative measures to capture district competitiveness. The alternative measures, however, are
rather indirect; some are not even based on congressional elections. Gulati (2004) averages three
indicators, presidential election returns, self-identified district partisanship, and congressional
race returns, to measure district competitiveness. Griffin (2006) uses changes in previous
presidential election results at the district level to measure competitiveness. These measures do
not tap into the subjective and dynamic nature of electoral vulnerability; some attempt to capture
competitiveness of congressional districts without using congressional election results. These
measures are different, but not necessarily better indicators than electoral margin.

Electoral vulnerability and responsiveness
There is a long-standing debate in the literature about the effect of electoral vulnerability on
legislative responsiveness. As discussed previously, recent evidence supports each of the three
possible relationships between vulnerability and responsiveness possibilities. A positive
relationship means support for the marginality thesis, that marginal members are more sensitive
to constituency preferences (e.g. Griffin 2006). The lack of a relationship, in the context of a
highly responsive legislative environment in recent decades, means that secure and marginal
members represent their constituencies equally well (e.g Gay 2007). A negative relationship

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means that intense competition may cause marginal legislators to be more responsive to their
own partisans instead of to their district median (e.g. Gulati 2004).

In this paper, I conceptualize and measure electoral vulnerability as a latent variable indicated
by current campaign spending in addition to other relevant variables. With this measurement, the
implications of the three possible relationships are somewhat different. A positive relationship
will still imply that vulnerability contributes to responsiveness, as the reversed causal relation is
unlikely. It is less plausible to argue that responsiveness produces vulnerability. The implication
of a negative finding, however, can be different. If a negative relationship is found, it is possible
that vulnerable members decide to appeal to partisans instead of district median, as discussed in
the literature. It is also possible that legislators may try to buy their way out of “out-of-step”
votes. In the latter explanation, legislators would first vote against constituency preferences,
knowing that doing so may increase their electoral vulnerability, but then try to compensate by
spending large amount of campaign for reelection in the hope that campaign spending may save
them from electoral misfortune. This explanation argues for a reversed causal effect, that is,
voting behavior leads to electoral vulnerability, instead of electoral vulnerability leads to voting
behavior.

When does vulnerability matter?
The literature has largely focused on whether or not electoral vulnerability affects policy
responsiveness. An important yet overlooked aspect of the effect of electoral vulnerability are the
conditions under which electoral vulnerability has a significant effect. Although aggregate-level
studies yielded mixed results, several individual case studies find significant effects of electoral
vulnerability. Bartlett (1979) finds that electoral margin is positively related to legislators' voting

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decisions on increase salaries for members of Congress. Jacobson (1993) finds electoral margin
has a strong positive effect on support for the 1990 deficit cutting bill.
Lanoue and Emmert (1999) find that multiple measures of electoral considerations had
significant effect over the House members' decisions on holding hearings for the Clinton
impeachment in 1998. The findings from the analysis of individual pieces of legislation suggest
that it is highly likely that certain conditions highlight the importance of electoral vulnerability in
the legislative decision-making process.

In this paper I hypothesize that three variables, issue area, timing of the bill, and general level
of support for the bill, are relevant to the effect of vulnerability. It is possible that bills in the
category of government operation, such as the case of the congressional pay raise bill, are
affected by electoral vulnerability. Governmental operation bills tend to only affect political
institutions; voters are therefore able to take a clear position of either supporting or opposing the
bills. Timing of the bills is also important since a hot topic near election time may attract more
attention than bills that take place at other times. The deficit cutting bill, the Clinton
impeachment bill, and the bailout legislation all occurred in a time close to a congressional
election, when vulnerable members may be especially cautious against controversial legislations.
Last but not least, if the general level of support to the bill is high, vulnerable members may be
more likely to jump onto the bandwagon to support the legislation.
Empirical Analysis

Measuring electoral vulnerability
I measure electoral vulnerability as a latent variable indicated by five variables: incumbent
campaign spending, challenger campaign spending, previous electoral margin, district partisan

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support, and seniority. District-level partisan support and incumbent seniority are also variables
that indicate incumbents' electoral vulnerability. District-level partisan support is the baseline
strength of incumbents' party among constituencies, and arguably the long-term force at work in
the absence of personal factors related to congressional candidates (see, Converse 1966,
Goldenberg and Traugott 1981). When district-level partisan support is strong, incumbents are
more secure from opposite party challengers. Seniority directly taps into the long-observed
phenomenon of incumbency safety, where incumbents win elections consecutively and arguably
gain electoral advantage over time (e.g. Mayhew 1974).2 Seniority may also contributes to
incumbents' subjective sense of electoral vulnerability. Holding electoral margin and campaign
spending constant, a junior member may feel more vulnerable compared to a senior, more
seasoned member of Congress.

Campaign spending is measured as all spending reported in the current electoral cycle; for the
109th Congress it covers January 2005 to December 2006, for the 110th Congress January 2007 to
December 2008. Electoral margin is measured as the percentage of vote share obtained by the
incumbents in the previous congressional election. If the election was a two-round system, vote
percentage from the first round is used. The first round vote provides a better indicator of the
incumbents' level of vulnerability, because it is an environment in which all candidates are
eligible to compete for votes. District partisan support is measured as the incumbent party's
presidential candidate vote share in the 2004 presidential election. Seniority is measured as terms
served in Congress.

2There is a long-standing debate about whether or not incumbents have been gaining electoral advantage over time.
For counter argument, see (Jacobson 1987).

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Statistically, incumbent spending and challenger spending are highly correlated. The reasons
are two-fold. First, both are indicators of incumbents' electoral vulnerability; second, incumbents
anticipate and react to challenger spending in election campaigns (e.g. Goldenberg, Traugott, and
Baumgartner 1986, Jacobson 1978). The correlation requires data reduction methods, in the case
of this paper factor analysis, that take into consideration variable correlation.

[TABLE 1 HERE]
Results of the exploratory factor analysis, presented in table 1, provide strong evidence of one
common factor underlying the five indicating variables; the factor has the expected relationships
with all of the indicating variables, although seniority seems to be a less relevant one.3 To
determine the number of latent factors, the “rule of thumb” Kaiser criterion is to retain factors
with eigenvalues greater than 1, since eigenvalues indicate the amount of variance accounted for
by each factor. The eigenvalue for the first factor is 1.49 and for the second one 0.47, which
suggests that there is most likely one common factor, and one factor only, that explains most of
the variance. Based on theories discussed previously, the common factor is electoral
vulnerability, which should have negative relationships with the campaigns spending variables
and positive relationships with previous electoral margin, district partisan support, and seniority.
The factor loadings confirm the directionality of the relationships, which suggests that the
common factor is indeed electoral vulnerability.4
Moreover, the absolute values of the factor loadings suggest that the campaign spending
variables are the most relevant indicators and seniority the least relevant one. This finding has

3For the sake of simplicity, only results of the 110th Congress are presented in table 1; results of the 109th Congress
are very similar.
4It is also possible that the signs of the factor loadings are reversed, where the estimated factor has negative
relationships with the spending variables and positive relationships with the other variables. A case like this is also
consistent with the theory; the estimated factor would be electoral security, instead of electoral vulnerability.

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two implications. First, it suggests that campaign spending variables need to be taken into
consideration in conceptualizing and measuring electoral vulnerability; previous electoral margin
alone could not fully account for variance of electoral vulnerability, which is subjective and
dynamic. Second, given the low factor loading (an absolute value of 0.23), high uniqueness (0.9),
as well as less theoretical importance of the seniority variable, it is not as relevant to the latent
factor of electoral vulnerability. Consequently, seniority is not included in the estimation of
electoral vulnerability in the next step.

[TABLE 2 HERE]
[FIGURE 1 HERE]
Table 2 presents the scoring coefficients of the variables in the estimation of the electoral
vulnerability score. The coefficients are rather similar between the 109th and the 110th Congress.
Ranking from the most important to the least important is challenger campaign spending,
incumbent campaign spending, previous electoral margin, and district partisan support. It is not
surprising that challenger spending is more relevant than incumbent spending in terms of
measuring vulnerability, because challenger spending is the less noisy signal. Incumbents engage
in preemptive spending even when they are safe; challengers do not have similar behavior.
When we observe the top five most secure and most vulnerable representatives from each
Congress, which are listed in Table A1 in the Appendix, the story of electoral vulnerability is the
story of “Happy families are all alike; every unhappy family is unhappy in its own way
(Tolstoy).” In the 109th Congress, the most secure legislators all won previous election with large
electoral margin and ran unopposed in the 2006 election. Among the most vulnerable legislators,
two faced strong challengers and were defeated in the 2006 election. One managed to survive the

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2006 election with a very close margin, and decided to forfeit the 2008 election to run for other
office. Two (Jim Gerlach R-FL and Melissa Bean D-IL) were incumbents who continued to
serve in the House after 2006 but had particularly tough races in the 2006 election. Their
electoral margins do not vary much over the years; for Gerlach it varies from 51% to 57%, and
for Bean 48% to 52%. Their campaign spendings, however, are much higher in the 05-06 cycle
than any of their previous or following elections.5 This is an example of how the dynamic of
incumbent's vulnerability can be much better captured by the spending variables.

Figure 1 shows the distribution of the estimated vulnerability score for each Congress. Most
legislators clustered around 0. Intuitively, one might suspect that there is a relationship between
electoral vulnerability and ideological moderateness, since anecdotal stories highlight the
vulnerability of moderate legislators such as bluedog Democrats. Using the absolute value of the
DW-NOMIATE score as the measure of ideological moderateness, the scatterplots presented in
figure 2, however, seem to suggest that there does not exist a relationship between electoral
vulnerability and ideological moderateness.

[FIGURE 2 HERE]
Electoral vulnerability and responsiveness
In this step of the analysis I examine the effect of electoral vulnerability on legislative
responsiveness. The dependent variable of legislative responsiveness is measured as each
representative's DW-NOMINATE score (Poole and Rosenthal 2000), which is derived based on
legislative roll call votes. There are four explanatory variables: legislators' partisan affiliation,
coded 0 for Democrats and 1 for Republicans; district ideological preferences, measured as the
Republican presidential candidate's vote share from the 2004 election; electoral vulnerability

5See figure A1 in the appendix.

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score, and the interaction term between electoral vulnerability and district preferences. I include
the interaction term so as to examine whether electoral vulnerability increases responsiveness.
The theoretical discussion of electoral vulnerability and responsiveness poses three possible
relationships. Each of the three possibilities has at least some empirical support. If the interaction
term turns out to be positive and significant in this analysis, it is evidence supporting the
marginality thesis, that is, more vulnerable members better represent constituency preferences.

[TABLE 3 HERE]
[FIGURE 3 HERE]
The analysis uses OLS regression with robust standard errors to account for
heteroskedasticity. Results presented in table 3 show that the interaction term is positive and
significant at 0.01 level, meaning that vulnerability has a positive effect on responsiveness. More
vulnerable members better reflect district partisan preferences in their own ideology. Figure 3
shows the increase of the marginal effect of district partisanship as vulnerability increases. It is
worth noting that, in spite of the change of majority party in the House from the 109th to the 110th
Congress, the effect of vulnerability on responsiveness persists to be positive and significant.
This is evidence suggesting that the effect of vulnerability does not depend on majority party
status.
Note that the substantive effect of vulnerability is fairly small; it is not surprising since
legislators' partisan affiliation and district ideological preference already account for most of the
variance in the dependent variable. A nested model using only these two explanatory variables
has R^2 values of 0.925 and 0.938 for the 110th and 109th congresses respectively. Legislators are
already highly responsive to district preferences; therefore, the additional effect of vulnerability

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on responsiveness is limited. However, the statistical significance and directionality of the effect
of vulnerability on responsiveness is clear, which is evidence supporting the marginality thesis.

Effect of vulnerability on roll call votes
The next step in understanding the effect of vulnerability on legislative behavior is to obtain a
more nuanced understanding of the conditions under which electoral vulnerability influences
voting decisions. The analysis consists of two steps. In the first step I regress each legislators'
vulnerability score on non-unanimous final passage bills voted in the 110th congress, and obtain
logistic coefficients of vulnerability on each bill. In the second step I let the regression
coefficient be the dependent variable, and use issue area, levels of bill support, and timing of the
bill to explain the size of the coefficients.6
The first step analysis uses logistic regression because of the binary nature of the dependent
variable. After controlling for partisanship and ideology, the results show that electoral
vulnerability has a statistically significant effect on 15 out of the 119, or 12.6% final passage
bills.7 This finding is consistent with previous results that electoral vulnerability affects
legislative behavior. In the second step, issue area is measured using the subject coding of the
Congressional Bill Project (Adler and Wilkerson 2008); levels of bill support is measured as the
total number of yea votes; and the timing of the bill is measured as the number of month into the
congressional session, which ranges from 1 to 24.

[TABLE 4 HERE]
Results in table 4 show that neither government operation issues nor civil rights and civil
liberty issues are related to the effect of electoral vulnerability. When there is a high level of

6This research design is similar to that of Bovitz and Carson (2006) in their analysis of the effect of individual roll
call votes on electoral outcomes. Instead of using statistical significance as the dependent variable, I use regression
coefficients, because the question of interest is what affects the size of the vulnerability effect.
7 In the appendix I list the bills and the vulnerability coefficient for each bill.

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support, electoral vulnerability is positively related to support for the bill. The finding is not
surprising in that vulnerable members are likely to be more sensitive to political conflict and shy
away from legislations when there is a close call. The sign of the bill timing coefficient is
negative,8 which suggests that vulnerable legislators may be less likely to support legislations
when the votes take place close to the election time. In future versions of the paper, I plan to
expand this section on the effect of vulnerability on roll call votes by using data from more
congresses and including additional explanatory variables.
Conclusion

This paper contributes to the literature in two accounts. First it sheds light on our
understanding of electoral vulnerability. When it comes to House elections, political scientists
have observed a decline of electoral competition and an increase of incumbents' winning margins
in recent decades. Some argue that the vanishing marginals increase incumbency safety and
decrease electoral responsiveness. However, representatives themselves are unlikely to agree to
the statement that elections are becoming easier and incumbents safer. One of the signs of
competitive elections is the increasing amount of money that goes into election campaigns from
both incumbents and challengers. To better understand and measure electoral vulnerability, we
should not focus on previous electoral margin as the sole indicator, but expand the measurement
to include important indicating variables of campaign expenditures.

Second, it is too early to conclude that electoral vulnerability does not affect legislative
behavior. Previous literature testing the marginality theory yielded mixed results; but it is likely
to be a result of inadequate measurement and not because of erroneous theory. With the more
robust measurement developed in this paper, I find strong evidence suggesting that electoral

8But it falls just short of achieving statistical significance at 0.05 level.

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vulnerability indeed increases legislative responsiveness. Vulnerability is not irrelevant, as some
suggest, and certainly not detrimental, as others argue, to legislative responsiveness. This finding
has important normative implications. Classic democratic theories rely on competitive elections
for accountability and responsiveness, which seems to be the mechanism at work in the U.S.
Congress.

To conclude, more research is necessary to further examine the relationship between electoral
vulnerability and legislative decisions, which is essential to representative democracy. Given the
normative importance of the topic, there has been surprisingly little research on this subject in
recent years. The next step of this paper is to further develop theories and empirical analysis to
examine the conditions under which electoral vulnerability affects roll call votes.

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19

Appendix

Table A1: Top 5 List

110th Congress

State District Name Electoral Incumbent Challenger
margin 06 spending 07-08 spending 07-08
California 33rd (thousands of (thousands of
New Jersey 10th
Pennsylvani 1st dollars) dollars)
4th
a 7th Most secure representatives 5.773
Illinois 0
Illinois 8th Watson, Diane E. 100% 229.692
4th 0
Washington 10th Payne, Donald M. 100% 502.611
Connecticut 14th 0
20th Brady, Robert A. 100% 1013.84 0
Illinois
Illinois Gutierrez, Luis V. 86% 188.438 4322.88
New York 413.001 3828.3
Davis, Danny K. 87% 3566.12
2852.51 5064.49
Most vulnerable representatives 3771.64
5444.41 7038.5
Reichert, David G. 51% 4904.27

Shays, Christopher 51% 4489.39

Kirk, Mark Steven 53%

Foster, Bill 55%

Gillibrand, Kirsten 50%
E.

109th Congress

State District Name Electoral Incumbent Challenger
margin 04 spending 05-06 spending 05-06
New York 16th (thousands of (thousands of
New Jersey 10th
California 33rd dollars) dollars)
23rd
Florida 8th Most secure representatives 0
Massachuset 0
6th Serrano, José E. 91% 314.38 0
ts 0
1st Payne, Donald M. 97% 495.562 0
Pennsylvani 22nd
a 8th Watson, Diane E. 89% 181.051 4097.66
13th
New Hastings, Alcee L. 100% 427.924 3386.54
Mexico 5226.16
Florida Capuano, Michael 99% 626.795 5058.73
Illinois E. 3002.8
Florida
Most vulnerable representatives

Gerlach, Jim 51% 3492.4

Wilson, Heather A. 50% 4906.6

Shaw, Clay 63% 4185.92
Bean, Melissa 52% 4294.59
Harris, Katherine 55% 8112.75

20

Figure A2: Dynamics of Electoral Vulnerability
Congressional Election Spending: PA 6th

Winner: Jim Gerlach

Congressional Election Spending: IL 8th

Winner: Melissa Bean
21

Table A2: Bill List

Coefficient of Bill title
vulnerability

0.60 Implementing the 9/11Commission Recommendations Act

0.72 Rail and Public Transportation Security Act

0.93 To provide Federal assistance to States, local jurisdictions, and Indian tribes to prosecute
hate crimes.

0.82 Department of Homeland Security Authorization Act

0.35 Department of Homeland Security Appropriations for FY 2008

Making appropriations for the Department of Labor, Health and Human Services, and
0.53 Education, and related agencies for fiscal year ending September 30, 2008, and for other

purposes

0.37 Departments of Transportation, and Housing and Urban Development and Related
Agencies Appropriations for FY 2008

0.85 Flood Insurance Reform and Modernization Act of 2007

0.68 Free Flow of Information Act of 2007

1.07 Saving Energy Through Public Transportation Act

0.50 National Highway Bridge Reconstruction and Inspection Act

-1.32 Paycheck Fairness Act

1.86 Commodity Markets Transparency and Accountability Act

-0.51 Employment Non-Discrimination Act (ENDA)
(Listed are bills in which vulnerability significantly affects voting decisions.)

22

Table 1: Exploratory Factor Analysis

Method: Principle Axis Factor # of observations: 436

Factor Eigenvalue Difference Proportion Cumulative
Factor 1 1.495 1.017 0.970 0.970
Factor 2 0.477 0.480 0.310 1.280
Factor 3 -0.003 0.195 -0.002 1.278
Factor 4 -0.198 0.032 -0.129 1.149

Factor Loading Factor 1
0.791
Variable 0.685 Factor 2 Uniqueness
Opponent spending 07-08 -0.451
Incumbent spending 07-08 -0.373 0.165 0.345
-0.233
Electoral margin 2006 0.341 0.413
District partisan support 2004
0.402 0.634
Seniority
0.357 0.732

0.210 0.901

(with 110th Congress data)

Table 2: Factor Analysis Estimation

110th Congress 109th Congress

Variable Factor Uniqueness Scoring Variable Factor Uniqueness Scoring
Loading Coefficient Loading Coefficient
Opponent
spending 0.794 0.369 0.481 Opponent 0.743 0.447 0.395
0.501 0.327 spending
07-08 0.706 0.823 -0.160 0.681 0.535 0.307
0.869 -0.138 05-06
Incumbent -0.419 -0.530 0.718 -0.208
spending Incumbent
-0.360 spending -0.527 0.721 -0.208
07-08
05-06
Electoral
margin Electoral
2006 margin
2004
District
partisan District
support partisan
support
2004
2004

23

Figure 1: Estimated Electoral Vulnerability
Figure 2: Electoral Vulnerability and Ideological Moderateness
24