I've always kind of assumed the deep divisions between (conservative) American Catholics and Evangelicals had mostly healed by now. But maybe that's due to my stance as an outsider: as a liberal Jew, it's difficult for me to differentiate between various conservative Christian sects from each other. This also might lead me to pervasively underestimate the amount of anti-Mormon sentiment Mitt Romney faces. He's conservative (today, anyway)! He's Christian! What more do you folks want?
And so, it appears my instinct might be mistaken. Running some numbers on the Iowa caucuses, Philip Klinkner finds that Huckabee has a serious Catholic problem. Despite his statewide victory, he ran into serious trouble in Catholic counties, who went strongly for Romney. I guess I have to ask whether or not the data is skewed by non-Catholic (and evangelical-heavy) areas just went hard against Romney because he's Mormon (while Catholics were less disposed to be automatically biased against him), but to my poorly trained eye it looks like Klinkner separated those variables out. Debaser raises the possibility that Catholic concentration in urban areas presents a confounding variable, which seems a legitimate point. But it wouldn't surprise me if Huckabee was at least underperforming among Catholics.
As Matt Yglesias points out, if true, this represents a problem for Huckabee. Catholics are the paradigmatic case of a voting bloc that is sympathetic to social conservatism but also likes their government programs. It's his platform personified. If he turns them off, he's going to have trouble making any serious progress in the general.