A wish for the future
Here's what I would like to see in the wake of a (potential) Dean withdrawal: Kerry should immediately invite Dean to stand with him and laud him publicly for all the great things he has done for the party. He should then say that, even more than Dean, the people who supported Dean should be proud of what they accomplished. His comments should be carefully geared NOT to sound condescending (this must not be a pat-on-the head for the little Deaniacs). He should then conclude with a promise that Deanizens will NOT be taken for granted, will not be ostracized and that any attempt to do so will meet with his swift disapproval.
Kerry has to make it clear that Dean and his supporters are NOT to be treated as enemies of the party. If he doesn't do this ASAP after Dean's withdrawal then the lingering pains of this campaign will grow into a festering boil. Things like that New Republic article about some Dean backers facing retribution should be setting off alarm bells in all Democratic circles.
I think there is a lot of bad blood between Kerry and Dean on a personal level. But if Kerry really wants to be the standard bearer of the WHOLE party then he has to be willing to put that aside and embrace the Dean forces. Anything less would be politically foolish.