it makes no sense to me at all why the democratic party leadership would want to cut lieberman any slack. the guy voluntarily left the party when he chose to run as an independent. after the 2006 election, the party needed lieberman to be a part of their caucus to get control of the senate (and thus hold the chairs of all of the committees). at that time lieberman had an actual bargaining position: he wanted his seniority to be honored by the dems and to become chair of a committee, the dems wanted lieberman in their caucus so they could achieve the magic number to be the majority in the senate. there was a clear quid pro quo and so in 2006 it made perfect sense for the senate democratic leadership would make concessions to keep him in the democratic caucus.
but after the 2008 election, the situation has completely changed. there are still a couple of senate races that haven't been called yet, but no matter which way AK and MN goes, democrats will be the majority in the senate with or without lieberman. simply put, they don't need him anymore. so he doesn't have any leverage to negotiate himself a chairmanship.
the fact that lieberman might contribute to getting the filibuster-proof 60 number shouldn't be a factor at all. the majority party of congress is decided by the size of each respective caucus. it's essentially a single vote, taken at the beginning of the congressional session. breaking a filibuster, on the other hand, can happen in any number of individual cloture votes during the next two years. a senator's caucus doesn't determine that senator's cloture vote, and it happens fairly often. they can always support a filibuster even when their party leadership is against it. nothing about keeping lieberman in the democratic caucus would require him to vote with his party on cloture.
once again, lieberman voluntarily left the democratic party. he also broke his promise to support the democratic candidate for president. and worse, he didn't just break his promise in a passive way by not doing anything to support the democratic nominee. he went further, actively campaigning for the republican candidate and joining in some of the smears of one of the nastiest campaigns in recent history. those are all serious strikes against him.
so what does benefit does the democratic caucus get by overlooking all of that and keeping him in the caucus? as far as i can tell, none. yes, lieberman still votes like a democrat on a few issues (he is, for example, pro-choice). but is he really such a prick that he will vote against his conscience on an abortion vote just because he's mad at the party that he dumped? besides, lieberman's one vote probably won't make a difference on any abortion-related vote. it's highly unlikely that lieberman would even be the deciding vote on cloture. there's no reason to let him keep his chairmanship under these circumstances.
