Probably the one main advantage Romney has over Guiliani and McVain is he at least realizes the need to reach out to the SoCon vote.
Romney's advantage is that's he a Governor, and all the Dem's have are Senators. If history is any clue that means he'd be a near certain winner.
I know a couple of people who have seen him speak and have said that he's electric in person and if the GOP has the presidency again, that person _has_ to be well spoken.