But if he had run as a Republican, he'd have my vote.
Actually, I don’t think he’d cause Romney to lose. I think the race would be between him and Romney. According to polls for years now the electorate is divided: left 23%, right 40% and middle 37%. (or thereabouts.)
What that means is in a 3-way race a conservative would have an advantage if the conservatives stuck together.
Mitt, though, has shown that he really wants to go after the middle-middle and the left-middle vote. He’d be going after some of Obama’s support, just as he really wants to do.
So, I think it would come down to the middle of the roader and the conservative.