What if it’s Romney vs. Obama in 2012?

Mitt Romney has two significant flaws as as Republican candidate:  Romney Care in Massachusetts and the fact that he is a Mormon, which is anathema to many committed Protestants and Catholics.  During the 2008 primaries, some people were saying that he was so flawed they couldn’t possibly vote for him, even if it meant abstaining and handing the election to the Democrat.

It’s possible that there will be a Romney vs. Obama match-up in 2012.  Do you think conservative voters will find themselves as constrained as they were in 2008, or has Obama proven himself to be so awful that any Republican who can make it through the primaries will get the vote?  How far will doctrinal purity go when the alternative is another 4 years of Obama?  (I framed this post around Romney, but ultimately the question goes to any Republican, no matter how flawed, versus Obama in 2012.)