I just finished reading "Red State, Blue State, Rich State, Poor State" and I am highly suggesting it as a very valuable and insightful look at American politics. I'm thankful that one of the more interesting trends they identified was put onto their blog: trends in religion and partisanship. Jews and non-Christians seem to show almost no real shift in partisanship over the years, and with the increase in non-religious and non-Christian voters this is a good sign for the Democratic Party's coalition. We are all familiar with the trend of Evangelical Protestants away from the Democratic Party and to the Republican Party, but I'd like to highlight the two other groups: Mainline Protestants and Catholics. Catholics seem to be trending Republican, while Mainline Protestants are actually trending Democratic.

Now look at the second graph. Note also that for non-evangelical Protestants, there's only a slight correlation between frequency in church attendance and support for the Republican Party. Born again Christians start out as more Republican and have a steeper slope in the correlation between church attendance and partisanship. Catholics are more similar to non-evangelical Protestants in that they have a smaller correlation. This just shows the trend for 2004, but the authors note that 2000 is generally similar.

There are a lot of things to observe here. First, Catholics are becoming more Republican over time, despite a growth in the share of Catholics made up by Democratic-leaning Hispanics. This argues for an even greater shift to the GOP by white Catholics. Combined with the pro-Democratic trend among Mainline Protestants, are we on the cusp of a "trade-off" in which Catholics and Mainline Protestants switch in their overall partisan loyalties? Is this trend at work when we see polls showing Obama competitive in historically Lutheran influenced North Dakota?

Also, consider the topic of why evangelicals are more pro-life than Catholics brought up by Ed Kilgore, Ross Douthat, and Megan McArdle. Ross I think gets it right, but I like how Megan explains it:

On the larger question, I think Ross is on the right track, but I might state it slightly differently: evangelicalism is self-selecting in a way that Catholicism isn't. Catholicism is as often a proxy for ethnicity as it is for belief; I observe Lent not because I believe in the risen Christ, but because my ancestors have done so for a couple of thousand years. Not that I self-identify as Catholic, but I know a lot of people who think of themselves that way even though their main connection to the Church is watching the occasional Hail Mary pass.

Evangelicals who stop believing in God, or biblical literalism, don't continue to call themselves evangelicals. The religion itself encourages forum shopping. Lukewarm Catholics, on the other hand, tend to stay put.

Despite Catholics showing less enthuthiasm for the pro-life cause as evangelicals, they are trending Republican. And this doesn't seem to be correlated with Catholic demographics changing with a rise in the percentage of Catholics with high church attendance; all Catholics tend to be more or less equally likely to vote Republican. Something seems to be shifting all Catholics closer to the Republican Party, parallel to an opposite trend among Mainline Protestants.

I think this gets down to issues of ethnicity and identity. Mainline Protestants, where they still linger on after the rise of secularism and evangelicalism, tend to be associated with a host of good government reformers in Greater New England. The identity of most Catholic voters seems to square up with the stereotypical white working class Reagan Democrat that Ross Douthat identifies as the new base of the Republican Party.