Here's something you don't see every day. Mitt Romney goes negative on Mike Huckabee in Iowa, and John McCain is the one who fires back on Huckabee's behalf. From a statement by McCain's Iowa chairman Dave Roederer that the McCain campaign sent out last night:

News that Mitt Romney will launch a new attack ad tomorrow is another move by a campaign that continues to insult Iowa voters. Iowa families should not be subjected to this negative style of campaigning, especially during the holiday season.

Governor Romney has flip-flopped on several major issues that voters care about. It's particularly amazing that Governor Romney would attack anyone on immigration when he's on his third position. John McCain has run an honorable campaign that all Iowans can be proud of. I call on Governor Romney to drop his plans for this negative attack and follow John McCain's lead. Candidates need to raise the level of the debate, not lower it.

Now part of this is definitely explained by the fact that, as Noam notes, McCain--like pretty much every other GOP presidential candidate--seems to despise Romney.

But I also think there's a fair amount of political calculation in McCain's chivalrous defense of Huckabee. Short of McCain winning Iowa himself, which isn't going to happen, a Huckabee win in Iowa is the best possible outcome there for McCain. First, a Huckabee win in Iowa would be a serious setback for Romney and would hobble him going into New Hampshire. Second, the McCain people seem to think that there's a natural ceiling on Huckabee's support in New Hampshire, and any momentum he got out of an Iowa victory would likely be felt in South Carolina rather than in New Hampshire. If McCain then went on to win New Hampshire--which he has to do if he wants to continues with his candidacy--that would probably be it for Romney. Giuliani, meanwhile, will have been shut out in the first two states, as well, and will be on the verge of being written off, setting up a McCain vs. Huckabee showdown in South Carolina. And, while the Son-of-the-South Huckabee would be a formidable opponent for McCain in South Carolina, I think the McCain people would rather go up against him than against Romney--for political as much as personal reasons.

--Jason Zengerle