It's Mike Huckabee, of course. This seems obvious where Mitt Romney is concerned: Huckabee's been slowly moving into a position to steal at least some of the Mittster's thunder in Iowa (with the aid of a friendly media, of course), and it's easy to imagine a strong Huckabee showing being played as the big story coming out of the caucuses, whether he wins outright or not, which in turn weakens Romney fatally in New Hampshire and lets Rudy slip past him.

But it's worth noting that in this scenario Huckabee probably dooms the Thompson campaign as well. Any Thompson narratives requires a win, and probably a big one, in South Carolina. And if you look at the polls there, Thompson's consistently around 15-20 percent, and Huckabee - who would seem to have natural Palmetto State appeal - is at 5-8 percent. That isn't a big gap, given Huckabee's low profile, and if he's the big story coming out of Iowa, and then New Hampshire is a fight to the death between Romney, Giuliani and McCain, doesn't Huckabee's momentum get concentrated in South Carolina? And doesn't it probably take a lot of votes out of Thompson's pocket, thus delivering the state, perhaps, to Rudy? At which point he coasts to the nomination, names Huckabee his veep, and together they win the general election - at which point Huckabee rips off his mask and reveals that he's really ... Bernie Kerik!

All of this assumes, of course, that none of Giuliani's rivals figure out a way to tear his candidacy to shreds.

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