And then there were four?

AND THEN THERE WERE FOUR?…. The Senate Democratic caucus will meet tomorrow to decide, among other things, what to do with Joe Lieberman. After a couple of weeks in which no one from the caucus was willing to say publicly that Lieberman should lose his committee chairmanship, all of a sudden, we have some significant movement in that direction.

First, Vermont’s Pat Leahy said he’d vote to take Lieberman’s gavel away. Soon after, Vermont’s Bernie Sanders, an independent who caucuses with the Democrats, said the same. Yesterday, Byron Dorgan of North Dakota said Lieberman’s conduct during the campaign was not “acceptable.”

This one, however, was unexpected.

Sen. Tom Carper (D-Del.), a close ally of Sen. Joe Lieberman, said the Connecticut Independent should pay a price for his campaign attacks against President-elect Barack Obama.

“There need to be consequences, and they cannot be insignificant,” Carper said in a Monday interview with The Hill. […]

Carper did not rule out stripping Lieberman of his coveted gavel running the Homeland Security and Governmental Affairs Committee, or imposing other sanctions like taking away seniority on other committees or a subcommittee on Armed Services.

Carper also noted that many of his Democratic colleagues are “very angry” with Lieberman for his behavior, adding, “I’m very disappointed as a friend and a colleague.”

This is something of a surprise because Carper was identified last week as one of four Senate Democrats who were a practical whip team for Lieberman, calling caucus members to urge other Democrats to support Lieberman’s request for keeping his committee chairmanship. The goal of Carper’s work, the Politico reported, was to “try to ensure Lieberman survives a secret ballot vote.”

It’s possible the Politico got the original report wrong. It’s also possible Carper’s attitude shifted in response to pressure from voters in Delaware. For that matter, maybe Carper wants there to be “significant” punishment, and for him, that constitutes a good, stern lecture for Lieberman about how betrayals aren’t nice.

But if Carper has switched from trying to help Lieberman avoid consequences to demanding that Lieberman face “significant” consequences, it seems like the “momentum” Lieberman had may be waning.