Disclaimer. Don't rely on these old notes in lieu of reading the literature, but they can jog your memory. As a grad student long ago, my peers and I collaborated to write and exchange summaries of political science research. I posted them to a wiki-style website. "Wikisum" is now dead but archived here. I cannot vouch for these notes' accuracy, nor can I say who wrote them.
Campbell, David E.; Green, John C.; Layman, Geoffrey C. 2011. The Party Faithful: Partisan Images, Candidate Religion, and the Electoral Impact of Party Identification. American Journal of Political Science 55 (January): 42-58.
American voters tend to vote for their party's candidate. That's not news. The question is, why? Political science has usually relied on three answers. The psychological approach says that voters support their party because of a deep, emotional, psychological attachment to it (see The American Voter). The rational approach characterized partisanship as a "running tally" of each party's past performance, so that partisanship varies with issue agendas and policy outcomes (see Downs 1957 and Fiorina 1981). The sociological approach focuses on the connection between social groups and parties (see Voting); if your friends all lean Democratic, you probably will too.
In a recent study, Campbell, Green, and Laymen use the sociological group-based approach to study how a candidate's religion influences voters. Suppose a candidate's message stresses traditional values, secure borders, and economic growth. We'd expect that candidate to appeal mostly to Republicans. Now, suppose we identified that candidate as an Evangelical. Given that Evangelicals are perceived as right-leaning, this group-based information cue should lead to even more Republican support.
This makes sense. Voters don't have enough time to learn everything they need to know about candidates, so they rely on information shortcuts instead--things like endorsements from outside interest groups. If voters know a candidate's religion, then we should expect them to use that information to infer other things about the candidate. The nice word for this behavior is "low-information rationality." The mean word is "stereotypical thinking."
Of course, knowing a candidate's religion won't always be helpful to voters. It only helps if the religious group is known to have certain political views. For example, consider this finding from Campbell, Green, and Laymen's article. In a 2006 survey, they asked respondents to judge whether (for example) Evangelical Christians are "mainly Republicans," "mainly Democrats," or a "pretty even mix of both." Here's what they found:
|"Members of this group are..."||Mainly Republicans||Pretty even mix of both||Mainly Democrats|
Okay. Those are interesting results. Contrast them with the correct answers (also from Campbell, Green, and Laymen's article):
|Reported 2006 Congressional vote:||Republican||Democratic|
We see that Mormons are slightly more Republican than Evangelical Christians (from the second table), but are perceived by voters as much less Republican than Evangelicals (from the first table). (I doubt that they would find the same thing if they ran this survey again; see my comments below.)
Likewise, Jews are just as one-sidedly Democratic as Evangelicals are Republican (in the second table), but they are perceived by voters as far more balanced politically than they really are.
We see that Evangelical Christians are perceived as an overwhelmingly Republican group. Other religious groups are not perceived as having a particular partisan leaning. Thus, we might expect that telling voters a candidate is an Evangelical would increase partisan voting: Republicans will like the candidate (because they infer he must be conservative), and Democrats will not (for the same reason).
Using a randomized survey, that's roughly what Campbell, Green, and Laymen find. If you present a hypothetical candidate to survey respondents, and you assign the candidate conservative views, then Republican respondents are much more likely to support the hypothetical candidate than Democratic respondents are. If you add in a note that this hypothetical candidate is an Evangelical, then the pattern sharpens.
By contrast, if you present a hypothetical candidate to survey respondents, and you assign the candidate liberal views, then Democratic candidates are much more likely to support the hypothetical candidate than Republican respondents are. But if you label this hypothetical candidate as an Evangelical, the pattern attenuates.
But this only works for Evangelical candidates, or for somebody generically identified as "religious." If you identify the hypothetical candidate as Mormon, Catholic, or Jewish, you don't see any effect. That makes sense: Voters don't have a clear sense of which way these religious groups lean politically, so these religious cues do not convey much useful information.
In short, then: Voters can use candidates' religion to infer their partisanship, but only for certain religions.
I would love to see a repeat of this study. These data were collected in 2006, with some additional data in 2007. I'm not sure that much has changed with Evangelicals, Catholics, or Jews since then, at least in terms of how they are viewed politically. But a lot has changed with Mormons. In 2007-2008, Mitt Romney ran for president. In 2008, Mormon involvement in California's Prop 8 was widely discussed. And in 2011, two Mormons (Mitt Romney and Jon Huntsman) are vying for the Republican presidential nomination. Voters have become much more aware of the rightward lean among Mormons. And if voters are aware that Mormons vote Republican at the same rate as Evangelicals, then Mormonism may have become a useful information shortcut.
Research on similar subjects
Campbell, David E. (author) • Green, John C. (author) • Layman, Geoffrey C. (author) • American Journal of Political Science • American Politics • Congressional Elections • Descriptive Representation • Experiment • Framing Effects • Low-information Rationality • Partisanship • Political Behavior • Public Opinion • Religion • Voter Information • Voting