Evan Bayh, of all people, nails it, via Mike Allen:
"He said things that were simply unacceptable, and I think he needs to apologize for that." Re Lieberman's chairmanship of the Homeland Security and Governmental Affairs Committee: "You have got to expect an apology, a sincere apology, and you have got to ... tell him: Look, we're going to give you a chance here. But if you don't do the right things as chairman, if you know, we see any continuation of this kind of behavior, well, then, ... the game is up at that point."
If Lieberman apologizes, he keeps his chairmanship, but he keeps it on a short leash, and if he backslides, Senate Democrats take it away from him. And if he doesn't apologize, well, then he loses his chairmanship right now. That seems to strike the right balance.