Douthat points me to this post by Mark Chaves, Professor of Sociology, Religion, and Divinity at Duke University. Chaves claims conservative white Protestant churches are less politically active than black Protestants or Catholics. This inspires Joe Carter to quip that political Evangelicals are "a herd of unicorns: powerful and abundant in the imagination while not actually existing in the real world." Chaves:
[N]otwithstanding extensive media coverage of political mobilization within conservative churches, conservative white Protestant churches do not stand out in their level of political activity. Catholic and black Protestant churches, overall, are more politically active than either liberal or conservative white Protestants. About three-quarters of Catholics and black Protestants attend churches that engaged in at least one of these eight political activities, compared to about half of white Protestants, either conservative or liberal (Synagogues’ political activity rates, by the way, are as high as the Catholic and black Protestant rates).
It is difficult to say why religious groups have such different political styles. Congregations in highly centralized denominations may do politics differently than independent congregations or congregations in decentralized denominations. Religious groups also focus on different issues, and perhaps different issues elicit different political strategies and tactics. More broadly, religious groups differ in the kinds of church-based political actions they consider appropriate. All of these factors probably shape a religious group’s political style.
In any event, differences among religious groups in how they do politics seem more important than differences in how much politics they do.
[W]e evangelicals still haven’t caught up on issues of the sanctity of life. Come to the annual March for Life held in Washington, D.C. every January and you’ll find fifty Catholics for every evangelical. For Catholics it is a moral, spiritual, and political issue. For evangelicals it nothing more than an emotional issue that we aren’t really dedicated to doing much about. I suspect that there were more evangelicals that participated in the recent Tea Party protests than have every participated in the March for Life. (And speaking of the Tea Party movement, could any evangelical group or groups ever muster that level of support about anything.)