An interesting poll from the Public Religion Research Institute.  It polls over 1000 people, but just over 800 of them are registered voters.  The methodology is explained, somewhat, through the link.  The poll gives Obama a 9 point lead over Romney, which I think is a bit high, but not so far out of the range of recent polls.  Obviously they were taken before Obama admitted his support for gay marriage.

TPM summarizes the religious breakdown as follows:

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%).

And while 16 percent of those polled believe that Obama is a Muslim, only 1 percent believes he’s Mormon.