TPM Reader CG
does some Joe-ology ...
Lieberman is in a very delicate political position. His value to Republicans, and his popularity with them, is that he is a Democrat who criticizes Democrats mercilessly. If he were to become a Republican he would quickly become just another RINO (Republican in Name Only) Senator from New England. His policy positions are, except for his intense support of any military action in the middle east, pretty middle of the road for New England and thus are well to the left of the Republican party. He would be just another Jim Jeffords or Lincoln Chaffee - and they both felt very uncomfortable in the Bush era Republican Party. And this is why he has continued to caucus with the Democrats.
But this has meant that Joe has had to walk a tightrope - he criticizes the Democrats enough to keep his popularity up with the Republicans, but doesn't go so far as to have the Democrats dump him from the caucus. He's played the thin 51-49 majority for all it is worth.
His recent actions, however, may indicate that Joe realizes he can't walk this tightrope forever. His popularity in CT is down near Bush territory, and with the Democrats likely to have a larger majority in the Senate come November, his leverage will be gone. My guess is that he realizes this is his last term in the Senate, and his last year with any leverage, so he's placing an all-or-nothing bet on a McCain victory. Joe is angling for either the VP slot or a high position in the McCain cabinet.