I love this woman.
I think Evan Bayh suggested that Joe Lieberman apologize for his behavior during the campaign for good tactical reasons that I agree with. If Lieberman doesn't apologize, which, at this point, I seriously doubt he would even consider, then Bayh and other moderate Dems have cover: they can claim that they were willing to welcome Lieberman back into the arms of the Dem caucus, they just had this one minor requirement that he apologize. If he doesn't, then they can claim that they were fair and open-minded, and he wasn't. They really have no reason to work terribly hard to try to keep him aligned with Dems.
Imagine if Lieberman actually switches sides and becomes a Republican. The one senator that I can think of who did that was Richard Shelby, from Alabama, who switched from being a Democrat to Republican a few years back. But he's from Alabama - he was moving with his constituents. Lieberman would be moving against his constituents. How comfortable is a pro-choice New England Jew going to be in a party dominated by southern Christians? The only Republicans among the Jews in the Senate are Norm Coleman, who might very well lose to a Democratic Jew, and Arlen Specter, who will probably retire soon. If he does convert, I don't think the RNC is going to be a lot of help in his next reelection campaign.
There's an outside chance that Lieberman would resign, which would mean that the governor of Connecticut would appoint a Republican, but I doubt Lieberman would do that. He could have exited gracefully in 2006 when he lost his primary.
It's nice being a Democrat and having the luxury of not really being too worried about whether or not we keep Joe Lieberman.