A couple days ago, Philip Klinkner posted this analysis of the county-level vote in Iowa and found that Huckabee did worse in counties with more Catholics. (Henry Farrell and Matthew Yglesias also noted Klinkner’s results.)
Some individual-level data would be nice here, if only to avoid (as Klinkner noted) ecological inference problems. Fortunately, the New Hampshire exit poll provides some. And the answer suggests that Huckabee does do a bit worse among Catholics than among other religious groups:
Huckabee did better among Protestants (12% of whom voted for him) and “other Christian” (26%) than among Catholics (7%). Catholic support was evenly split between Romney and McCain. But it remains to be seen whether this “Catholic gap” is (1) big enough to be problematic and (2) durable, if Huckabee works to appeal to Catholic voters.
[Original post analyzed Romney, not Huckabee, for some reason. Thanks to commenter Sam for pointing this out. Clearly, I need to blog less about the election.]