These various fears and paranoias are nourished by the fact that America’s churches are increasingly too institutionally weak, too fragmented and internally divided to bring people from different political persuasions together. About 75 percent of Mitt Romney’s co-religionists identify as Republicans, and it’s safe to assume that President Obama didn’t meet many conservatives in the pews at Jeremiah Wright’s church. American Catholicism still pitches a wide enough tent to include members of both parties, but the church has long been divided into liberal and conservative factions that can seem as distant from one another as Rush Limbaugh and Bill Maher.

In this atmosphere, religious differences are more likely to inspire baroque conspiracy theories, whether it’s the far-right panic over an Islamified United States or the left-wing paranoia about a looming evangelical-led theocracy. And faith itself is more likely to serve partisan purposes — whether it’s putting the messianic sheen on Obama’s “hope and change” campaign or supplying the storm clouds in Glenn Beck’s apocalyptic monologues.

Americans have never separated religion from politics, but it makes a difference how the two are intertwined. When religious commitments are more comprehensive and religious institutions more resilient, faith is more likely to call people out of private loyalties to public purposes, more likely to inspire voters to put ideals above self-interest, more likely to inspire politicians to defy partisan categories altogether. But as orthodoxies weaken, churches split and their former adherents mix and match elements of various traditions to fit their preferences, religion is more likely to become indistinguishable from personal and ideological self-interest.