There seems to be a consensus forming that the best solution to l'affaire Lieberman is to allow him to continue to caucus with the Democrats but to strip him of his chairmanship of the Senate Homeland Security and Government Affairs Committee. Let me explain why this is a reasonable, but inadequate, punishment.

It's a reasonable punishment, in that it takes something tangible away from Sen. Lieberman without doing the equivalent of cutting off one's nose to spite one's face. Having Lieberman might provide the Democrats with a very real benefit...but it isn't what you think it is.

It comes down to the partisan weighting of committees. Right now, with a 51-49 split, the Democrats have exactly one more seat than the Republicans on each of the Senate committees. If the Republicans remain united and they can pull a single defector out of the Democratic side, they can prevent committees from sending legislation to the floor. Now that the Democrats have (at least) 56 seats (not including Lieberman) they can rearrange the weighting so that Democrats have two more seats than the Republicans on all the committees. But if the Democrats reach 58-60 seats, they will have an argument for three more seats on the committees. That's where Lieberman can add value by remaining in the caucus.

It's actually a very complicated problem to solve. Technically, as long as the Democrats lack sixty votes, the Republicans can veto any attempt to re-weight the committees. But, respecting precedent, the Republicans will concede at least a two seat deficit. The question is whether they can be bullied into conceding a three-seat deficit. I don't have a resource to tell you the historical cut-off points, but there have been three seat differentials with less than sixty seat majorities in the past. This, then, is the strongest argument in favor of allowing Lieberman to caucus with the Dems.

He must be punished in some way, however, and losing his committee chair is the bare minimum. The problem is, it's not enough. Lieberman sits on three other committees: Armed Services, Environment & Public Works, and Small Business. I have no problem with Lieberman working on infrastructure, environmental issues, and small business, but he must not be allowed to continue on serving on the Armed Services committee. He will be a Republican voter on the committee and an obvious ally of the Ranking Member, John McCain.

Lieberman cannot be trusted to sit in on strategy sessions related to national security. He simply cannot be allowed to stay on Armed Services, or to serve on other intelligence related committees. That should be the penalty. He can take it or leave it. He can caucus with the Republicans if he wants. He'll probably vote the same way 99% of the time regardless of which party he caucuses with. He's as likely to filibuster as a Democrat as a Republican. His only use to the Democrats is theoretical (that he might lead to an extra seat per committee). That's worth something and he doesn't need to be expelled, necessarily. But he does deserve worse than merely losing his committee chair.