Well, for me, it is more than just his poor delivery or his performance style. He opposes many of the things that I think will make this country a whole lot better. I can see supporting Hunter, but Fred doesn't support a state abortion ban, opposes the Marriage Amendment, opposes Tort Reform, won't sign the No New Taxes Pledge etc...And I still feel uncomfortable about his tendency to side with the McCain gang.
The bottomline is that time will not change the fact that I don't agree with Fred's positions. Romney's positions more closely align with mine (and the GOP platform). Of course, if Fred happens to win the nomination, I will whole-heartedly support him. Our guys are far better than any of the dem candidates. Mitt just happens to be the best IMO.