I've heard it rumored that this is purposeful tactics by the party itself..
-It is supposed to draw back far-lefties they lost to third parties for running Bush-lite Kerry.
-It is supposed to shame shallow young voters who ride the fence and make them lean toward the Democratic party as 'image'.
-It is supposed to temporarily cement a 'hard-left' stereotype of Dems to pave the way for a more moderate candidate in 2008.
In the end, the main people they offend would never have voted Dem anyway, they gain some back, and the guy they run in 2008 looks more palatable to EVERYONE compared to Dean. I think it is BS, but that is what people are saying.