This new poll has some interesting data on how different religious groups are viewing the presidential election. Here's the summary (HT TPM):

White evangelical voters strongly support Romney over Obama (68%vs. 19%). Catholic voters overall say that they would be more likely to vote for Obama than Romney (46% to 39%), although white Catholic voters favor Romney over Obama by a significant margin (48%to 37%). Obama has an advantage over Romney among white mainline Protestant voters (50% vs. 37%) and religiously unaffiliated voters (57% vs. 22%).

I assume that the Obama lean among Catholics is largely due to the turn away from the Republican party by Latino voters.