Jamie has an online article making the case for why Joe Lieberman should get to keep his position as chairman of the Homeland Security Committee in the Senate. I did not find his case persuasive.
The premise of Jamie's argument is that some liberals are proposing to punish Joe Lieberman for being a moderate Democrat. For instance, he writes,
Yes, Lieberman's frequent and vocal complaints about the Democratic Party have irked his colleagues. But, in terms of policy, has he really damaged liberal aims more than the other Democratic congressmen and Senators who have not toed the party leadership's line? ... a political party that seeks to represent a broad swathe of the country should be able to accommodate someone (even a committee chairman) who holds slightly divergent views from the congressional leadership. For an example of what happens when a political party imposes ideological purity tests Democrats need only cast their gaze across the aisle.
But Lieberman is not facing potential punishment because he has criticized his own party or failed to uphold its agenda. As Jamie points out, that is common behavior, and it would be highly unusual for Lieberman to be sanctioned for it. What Lieberman did was to endorse and campaign for the other party's presidential nominee. What has further upset Democrats is that, in their view, Lieberman promised to confine his role to praising McCain, but went beyond that to attack Obama.
For a Senator to endorse a member of the opposing party is extremely rare. The last instance I'm aware of is 1964, Mississippi Representative John Bell Williams and South Carolina Rep. Albert Watson, both Democrats, endorsed Barry Goldwater for president. After the election, they were stripped of their seniority. Doing the same to Lieberman would be following this precedent, not some unusual retribution. In any case, for Jamie to discuss the Lieberman issue as though he were a regular moderate being subject to an ideological litmus test bears no relation to the reality of what happened. It would be like defending Ted Stephens on the grounds that Senators should be allowed to improve their homes -- imagine what would happen if every Senator who underwent home renovations were driven from public life, etc.
Jamie proceeds to argue, "Pointedly, not a single Democratic senator has publicly called for stripping Lieberman of his committee chairmanship or expelling him from their caucus." I'm not sure how he reaches that conclusion. He links to an article stating that some Democrats are supporting Lieberman, but the article does not say that no Democrats are opposing him. Indeed, Pat Leahy (explicitly) and even his ally Tom Carper (implicitly) have called for stripping Lieberman of his chairmanship.
The case that's being made against letting Lieberman keep his committee has nothing to do with "punishing moderates." It's that losing one's seniority is the normal consequence for endorsing the opposing party's presidential nominee. I don't actually feel very strongly about that either way. The more compelling case, in my view, is that Lieberman seems to be consumed with rage at the Democratic Party. That's why Lieberman asserted that Obama "has not" put his country first, speculated that Hamas would favor his election, and said that it's "a good question" whether Obama is a socialist. These statements were more extreme than even many Republicans were willing to make. To give subpeona power over the Executive Branch to somebody who endorses wild partisan criticisms of the president would be very risky for Obama.
Update: A reader points out that Lieberman speculated that obama might be Marxist, not a socialist. And jamie points out that Leahy and Carper had not yet spoken out against Lieberman when he wrote his piece. (Though it does make his point inoperative.)