I fear Huckabee.
Of all of the GOP candidates I see him as the one most likely to defeat a Democrat in '08.
Not just because, as Kos points out, his base can get out the vote. But mostly because of Huckabee's entertainment value.
Huckabee is quite simply very entertaining. He is witty, personable and a terrific speaker (not to mention an accomplished musician). I maintain that elections have come to be almost all about entertainment, that what shows up on TV - sitcom, talk show or candidate - is perceived as all being of a piece; and that so many voters will simply vote for the most entertaining candidate. Thus Bush's "victories" (I think he lost both elections, but..) - the more of an idiot he was shown to be, the more entertaining and thus electable he became. Certainly he was far more entertaining than (the 2000 edition) Gore or Kerry.
Add to Huckabee's entertainment value (not the least of which are his absurd views on evolution, etc.) the fervency of his supporters, and he will pose a difficult challenge.
His GOP primary opponents are for the most part (Paul excepted) astoundingly boring, and I think with the "boost" his Iowa win will give him, he'll get the GOP nomination.
I'm pretty confident Obama would defeat Huckabee in the general, given that Obama is himself quite entertaining (great speaker, interesting racial background, young and good-looking, etc.) and of course that his views are the more widely shared. But I fear that Edwards (who appears humorless) or Clinton (who is) would not fare so well against him.
We should resist the temptation to condemn Huckabee to the electoral dustbin because his positions are out of the mainstream. They help make him entertaining, and that I suggest is perhaps a politician's biggest asset today.