First, Ezra did not support Lamont.

In the comment you linked to, he says that he 'supported Lamont's challenge'. On his blog at the time this was posted. I know you disagree with him, but are you actually accusing him of lying? And of posting stuff to his blog that he actively disagreed with but didn't take issue with?

Second, Lieberman was elected FROM the Right in 1998.

Or 88, even. And he was elected from the centre with assistance from Republicans, like Buckley, who disagreed with him, but wanted to punish Weicker. And since the Republicans effectively expelled him, Weicker has moved more to the left. They had little leverage left over him. It's a mirror image of what's happened to Lieberman.

Third, in 2003, Lieberman was running for the Democratic nomination for President.

Exactly. At the point at which he was seeking the most popularity within the party he was most left wing.

Fourth, WHEN Lieberman was primaried he moved to the LEFT.

After moving back to the right following his failure to get the nomination, but yes. It's the same point as the last one. When he wanted the party to back him he became more left wing. Which was why primarying him was a good strategy, provided we then won AND then beat him in the election. Failing to do this meant that he owed the Dems much less than would otherwise be the case. If it wasn't for his desire to keep his committee chairs and get a certain amount of pork Reid would have virtually no leverage over him at all, assuming he's given up the idea of running as a Dem ever again.

Fifth, before Al Gore tapped him for VP in 2000, Lieberman was well to the Right. Then he stayed in the center because he had delusions of being the Dem nominee in 2004.

Yes. When he thinks he will get a reward from it he moves to the left.

You really know nothing about Lieberman.

Never met the man. Nonetheless, based on his record, I'd agree with Ezra that

The ideological prism is inadequate for understanding Lieberman. His dysfunctions are less principled than pavlovian. If his instincts are centrist, his fans are Republican. Long a reflexive compromiser, the first to condemn Clinton on the Senate floor, he gave liberal Democrats no reason to enthuse over him but offered nervous Republicans much appreciated cover. And they were appropriately grateful. So though Lieberman is a Democrat and close with his Senate colleagues, he's long understood that the good vibes and friendly tones emanate, for him, from the right. So when he faced off against Cheney, he was speaking to a friend of sorts. Like in the past, a compromising stance towards the right would result in the gush of admiration he never got from the left. And so he did as humans tend to, blindly groping towards the easy praise and away from the tense confrontation.

Fast forward to tonight. Lieberman is angry, sharp, testy, quick. Why? He knows this audience dislikes him, that there's no love to be gained by sucking up to Ned Lamont. So he won't. Instead, he'll destroy his opponents, seek total triumph over those who dislike him. It's easy to attack those who hold you in contempt. And that's the impulse that defines Lieberman's Senate career: the left doesn't like him, so he reacts, naturally, with disdain and indifference. He didn't want any of those sour ol' grapes anyway! But Hannity and Bush and all the others shower him in praise and affection, and given the waves of opposition rippling from his left, he can't alienate his fans and supporters on the right. It's human nature to seek encouragement and refrain from angering your allies, so that's what he does. Unfortunately, his allies are loathsome.