Publius at Obsidian Wings points to moderate Utah Governor Jon Huntsman as a potential 2012 Republican nominee. He notes that Huntsman will probably have the moderate side of the track pretty much to himself as Sarah Palin, "Bobby" Jindal, Mark Sanford, Mitt Romney, and Mike Huckabee all clump together on the conservative side, chasing the same pool of conservative "base" voters.
Publius ends his rumination wondering whether it's even possible for a moderate to win the Republican nomination at this point in the party's downward spiral, but I think it's not so improbable. After all, plenty of states have open primaries, so Huntsman will be able to count on the votes of unaffiliated moderates. And given that most of the GOP's primaries are winner-take-all, Huntsman could very well end up with a majority of delegates on the strength of those unaffiliated crossover voters.
Which would leave him . . . where? Well, as commenter superdestroyer points out, Huntsman's moderate positions on issues like, say, immigration reform (or, as wingnuts like superdestroyer call it, "open borders") put him at odds with the GOP's ever-smaller-and-more-extreme base. So what you'll end up with is a moderate candidate facing a convention (and party) that hates his guts. In order to avoid the problem of an unenthusiastic base, Huntsman would have to do what McCain did: choose a running mate that the base likes but the rest of the country finds appalling. McCain tried to square the circle by keeping Sarah Palin confined to her invitation-only Nuremburg rallies and hidden away from the sane three-quarters of the country, but it didn't work. The crazy leaked out and poisoned his campaign.
If Huntsman does win the nomination, he'll need to solve his version of the Palin Problem. And he's only got three and a half years until the 2012 Republican National Convention, so he'd better think fast.