The Clintons are still ticked that Howard Dean and Obama stole the party leadership away from them.
They know that if Obama loses (which they dearly hope happens), Dean is done as well and the Clintons reassert themselves as party leaders. There’s no one else in line to take the helm.
They have to take out more than just Dean. They’ve got to destroy or neutralize the faction of the party that forced Obama into the nomination. That includes Reid and Pelosi and a bunch of others. If today’s quotes are any indication, they’re out for blood.