I think you're right. Neal Boortz, whom I listen to very little, put this pretty succinctly when he said that Clark's job is twofold---take the momentum away from Dean, and don't get too powerful himself. I think that's about right. Certainly he doesn't have to worry about the latter, and it does appear he has thrown off Dean.
But the fascinating thing is that the "no-enemies-on-the-left" mantra of the Dems keeps EVEN DEAN from responding to this direct assault on him by the Clintons! How long will he put up with it?