I can invision the DIM party splitting in half in the next couple of years. I don't expect it though, the people at the top know how to do just enough to 'passify' the extremists just enough to keep them in line.
In a worst case senario for them, 10 - 15% of the party will go Green, or invent a totally different party behind some left wing leader.
The choosing of their next chairman could spawn a blood-bath, that will destroy them. It will be fun to watch!
Go over to the DU and check this thread out: http://www.democraticunderground.com/discuss/duboard.php?az=view_all&address=104x2798390. The left is already fighting amongst themselves over whether Howard Dean is a good thing for the Democrats. Hilarious! It will only get better as 2006 gets closer. The extremists already control the Democratic base, and they will lead the liberals off another cliff in 2006.