Yet More on Lieberman

This seems largely correct to me:

So why is he doing this? Because he’s bitter. According to former staffers and associates, he was upset by his dismal showing in the 2004 Democratic presidential primary. And he was enraged by the tepid support he got from many party leaders in 2006, when he lost the Democratic primary to an anti-war activist and won reelection as an independent. Gradually, this personal alienation has eaten away at his liberal domestic views. His staff has grown markedly more conservative in recent years, and his closest friends in Congress are now Republicans John McCain and Lindsey Graham. For Lieberman, the personal has become political, and it has pushed him further to the right.

There are two ways of reacting to this argument. On the one side, you can treat it as an accusation that liberals are "to blame" for Lieberman's lurch to the right. The altogether more sensible way to take it is that the campaign to unseat Lieberman by supporting Ned Lamont had the foreseeable consequence of pushing Lieberman to the right if he managed to win anyway. As Ezra argued, the primary forced Lieberman to find an electoral coalition that was far more right wing than the one he had previously assembled, and it's natural that he'd be more responsive to that coalition after the election. But as Beinart suggests, politicians aren't simply vote-seeking automatons. It's not surprising that Lieberman reacted to harsh criticism with bitterness, and consequently with a shift farther to the right.

None of this means that supporting Ned Lamont was a bad idea. First, it was unlikely that both of the above conditions would hold. Had Lieberman won the primary, he might have been bitter but he would have been responsible to the same electoral coalition. Having lost the primary, it was unlikely that he was going to win the election, but unlikely things do happen in politics. Second, Ned Lamont would have made a much better, and much more progressive, Senator than even the pre-2006 Joe Lieberman.

The institutional failure, I think, was that the Democratic Party didn't fully understand that it needed to put Joe Lieberman's political career in the dirt in 2006. I think they believed that the choice was essentially between two Democrats, rather than between a Democrat and a guy who was going to be elected by Republicans and was going to loathe the party's progressive base.