Romney actually can bring in votes, too. There are decent-sized Mormon populations in some western states that are have been becoming less red and that Obama thinks he can take in lieu of Ohio and Florida. A similar effect with Lieberman and the Jewish vote helped make Florida closer than one would otherwise have expected in 2000.
Romney also has family history and a good vibe in Michigan — he won the primary there — and the credibility to make the argument that the Dems are to blame for the auto industry decline. Winning Michigan would be pretty big for the GOP.
Mitt would be great. He will make mccain look like an urchin, but then anyone would.