Religious identity is something that is being seen more and more as an indicator for party preference. David French of The Washington Post's "On Faith" blog, believes that the social conservative agenda surrounds one issue: abortion. Some political scientists will generally agree with him, citing that the Republicans are notorious for using wedge-issues to get themselves into elected office.
French then goes on to write:
It’s no secret that American politics are polarized, and as one political party is increasingly identified by faith, the other is increasingly secular. In the last several election cycles, church attendance has been a leading indicator of voting preference. The more often a person goes to church, the more likely they are to vote Republican. The less often they attend, the more likely they are to vote Democratic.
This is a terrible development for faith in America. Even worse, it is unlikely to change. The combination of faith identification and party identification has created a profound barrier not just to dialogue but also to basic civility. The famous “Jesusland” meme created after the 2004 election is just one manifestation of the contempt generated by the political and religious polarization.
This is where I will disagree. The people are not exactly polarized, it's the political elites that are more differing. The other point to make here is that the Democrats are not exactly secular.
Being religious and being a Democrat is still acceptable. In fact, I'd argue that it's still not exactly acceptable to be non-theist in some parts of the Democratic party. Many Democrats differ on some issues of church and state, with most leaning in a secular approach. Democrats at the state-level in Indiana, are generally pro-life because Indiana Right to Life was founded by a Democrat. Rep. Joe Donnelly (D-IN) is also pro-life. So the abortion issue is not exactly a religion one, in the case of Indiana.
When it comes to being non-theist within the party, it's accepted to a degree. Let me start here with saying that there is only one openly non-theist member of Congress: Rep. Pete Stark (D-CA). Outside of Rep. Stark there are many closeted members within the Democratic party. Some might hide their preference to retain office in more religious areas, others may hide their beliefs because of internal norms. While it may be acceptable to support church and state separation, there's still a problem of identification because it's still seen as a stigma.
Even if the United States is a center-right country, levels of religiosity are decreasing. Republicans are siding with the Religious Right, and the shrinking demographic of the highly-religious. This strategy will bite them eventually, and that may very well happen in 2012. The Democrats on the other hand have an even harder task with religion. Although they are mostly in favor of church and state separation, there is still a stigma towards being non-theist within the party. Until more candidates run for office as openly non-theist, the Democrats may continue to be viewed as a "safer" option rather than the "safe" option by non-theists.
(Via The Washington Post)