As Steven Taylor notes in the latest edition of the Toast-O-Meter, Howard Dean is leading the other Democratic contenders in a lot of national and state polls, including in the key early primary state of New Hampshire, even while his rivals—most notably Joe Lieberman—step up their attacks on him.

So far, attacks from the remainder of the pack have had little effect; however, if this AP account from the campaign trail in Iowa is to be believed, Dean may be starting to feel some heat:

Howard Dean appealed to fellow Democratic presidential candidates Saturday to stop the bitter attack politics that have come to dominate the race for the party’s nomination. The race needs “a little character transplant,” he said.

“It’s not necessary to tear down the other opponents,” said Dean, whose front-running campaign has come increasingly under fire from Democratic rivals.

However, it may be too late for his rivals to do anything about Dean’s long march to the nomination. It’s December 20th, only five weeks before the New Hampshire primary, and all the members of the ABD faction are still in the race, which—as I’ve explained before—is deadly to their collective chances of stopping Dean from gaining the nomination. The electoral rules are clear on this point: the more ways the anti-Dean vote is split in a state, the more delegates Dean will receive. Make no mistake: coalescing around a single ABD candidate won’t stop the Deaniacs’ lemming-like procession behind their leader, but it will mean that credible candidates will get more delegates—you need 15% of the vote in a Congressional district to get delegates, and judging by the polling numbers the only candidates who will be able to do that consistently are Dean and Sharpton, the latter due to the effects of majority-minority districts.

The bottom line: Lieberman, Kerry, and Edwards need to step aside today and let Clark and Gephardt have a fighting chance to get enough delegates between them to stop Dean, or it’s going to be a very long year for Democrats.