weco,
You make the assumption that such people were on Romney's side in the first place. I think that's foolish. The fact that Romney is not Christian is one of the FIRST "negatives" that came out. Nobody is going to back away from him for that NOW.
But if they were inclined to drop him because of his faith, where would they turn? What's the alternative? Do you seriously think God-fearing, Bible-thumping Christians would abandon Romney for OBAMA? Oh, please. Nobody likes or respects Obama for his religion. NOBODY.
So, we've got a Mormon -vs- a pro-abortion Atheist/Agnostic/Bad Christian/Muslim (Take your pick. He's ONE of these.)
My guess is that Bible-thumping Christians will grit their teeth, wish that Rick Santorum were still in the race, then pull the lever in overwhelming numbers for the guy who goes to church and doesn't condone baby slaughter.
Now, this is mostly my opinion, and you're welcome to reject it (I'm sure you will.). But the likelihood that I'm wrong on this is very nearly nil. I think you know that too since you're no dummy. Just look at how the candidates are polling in the Bible Belt.
BTW, per this map, the only state Obama is losing that he won in 2008 is Indiana. And there are none that he's gained (though Wyoming is LESS RED than it was in 2008.)
In addition to Wyoming, the following are up for grabs: Oregon, Colorado, Iowa, Wisconsin, Ohio, Virginia, North Carolina, Florida and New Hampshire. In 2008, every one of those states went Obummer's way.
Fat chance of that happening again.