Michael Illions is keeping a vigil. He’s certainly right that Lieberman has threatened before to switch parties if the Dems do anything overly defeatist. From February:

“I have no desire to change parties,” Lieberman said in a telephone interview. “If that ever happens, it is because I feel the majority of Democrats have gone in a direction that I don’t feel comfortable with.”

He seemed to suggest in the same interview that funding was the key, not a timetable for withdrawal, but “direction” can of course mean a lot of things. Indeed, he’s got an op-ed in WaPo this morning that might, if one were so inclined, be read as a shot across the party leadership’s bow:

[T]oday, perversely, the Senate is likely to vote on a binding timeline of withdrawal from Iraq.

This reaction is dangerously wrong. It reflects a fundamental misunderstanding of both the reality in Iraq and the nature of the enemy we are fighting there…

When politicians here declare that Iraq is “lost” in reaction to al-Qaeda’s terrorist attacks and demand timetables for withdrawal, they are doing exactly what al-Qaeda hopes they will do, although I know that is not their intent…

The challenge before us, then, is whether we respond to al-Qaeda’s barbarism by running away, as it hopes we do — abandoning the future of Iraq, the Middle East and ultimately our own security to the very people responsible for last week’s atrocities — or whether we stand and fight.

To me, there is only one choice that protects America’s security — and that is to stand, and fight, and win.

He won’t flip. Coming from a state as blue as Connecticut, it’d make his prospects for reelection in 2012 exceedingly dim. Only if he’s approaching this issue the way McCain is, as something worth gambling his political future on, would he make a move like that. Also, what would switching parties achieve vis-a-vis Iraq? He already votes with the GOP on war measures so they’re not picking up any votes that way. It’s also my understanding that the committee chairmanships wouldn’t change. It’d be a purely symbolic gesture with far greater costs than benefits. Finally, if he bolts, the Dems might well be able to engineer a counterbolt among some anti-war GOP senator. Hagel and Gordon Smith from Oregon would be the obvious candidates.

In any case, Liebs isn’t going to do this with Bush promising to veto the bill anyway. If the Dems come back with some alternative after the veto that’s equally recalcitrant, then maybe. But not today.