This writer has worn out several computers criticizing Senator Joe Lieberman, going back to the days when he was mounting a conservative-backed challenged to progressive Republican Senator Lowell Weicker. In 1988, Lieberman was a Democrat in good standing with a party that was willing to defeat one of the nation’s leading liberals in order to secure a minimal partisan advantage.

Now, Lieberman is a free-floating independent — having been reelected, after losing his 2006 Democratic primary, as the standard-bearer of an ego-trip party called “Connecticut for Lieberman” — who caucuses with the Democrats.

On foreign-policy issues, Lieberman is more neo-con than the neo-cons. On economic policy, he is, like Indiana’s Evan Bayh and a number of other senators, a Democratic Leadership Council corporatist with a slight sympathy for trade unionism. On social policy, he’s a moderately liberal mainstream Democrat.

During the course of the 2008 presidential race, Lieberman chose to follow his neo-con instincts and back Republican John McCain, the Arizona senator with whom he shares a passion for a long-term U.S. presence in Iraq.

Lieberman’s ridiculous appearance at last summer’s Republican National Convention should have been sufficient punishment for the senator from Connecticut. After all, the man who was himself the Democratic nominee for vice president in 2000 had to try and find nice things to say about McCain’s veep pick, the absurdly unqualified Sarah Palin.

But there are many Democrats who now propose to purge Lieberman from the party’s Senate caucus — a move that would strip him of committee assignments and the advantages that accrue to a senior senator serving with the protection of the majority party. The issue will come to a head in short order, as the new Senate majority determines whether to kick this particular senator out of the club.

Were I a senator, I’d oppose the purge.

It is not that I have any particular taste for Lieberman or his policies. I have interviewed the man a number of times and covered him in many settings and, frankly, he has always impressed me as a self-serving petty moralist who is a bit too bemused by himself — and who is, of course, as consistently wrong on trade policy as Rahm Emanuel and as consistently wrong on Afghanistan as Barack Obama.

But it strikes me that purging members from caucuses never looks very good and never has the desired effect of achieving the ever-illusive goal of ideological purity.

As putrid as it has been on so many matters in recent years, the Senate Republican Caucus has actually understood this fact. In 2004, when Rhode Island Republican Senator Lincoln Chafee announced before the presidential election that he would not be voting to reelect George W. Bush, there was plenty of grumbling among conservatives. But Republican Senate leaders immediately made it clear that Chafee would not be punished; in fact, they maneuvered, unsuccessfully, to try and get the Rhode Islander reelected in 2006.

Republicans weren’t so smart in the 1950s. After Oregon Republican Senator Wayne Morse announced before the 1952 presidential election that he would be voting for Democrat Adlai Stevenson — the GOP caucus stripped Morse of his committee assignments and effectively forced him across the aisle to a Democratic caucus that Lyndon Johnson was slowly but surely turning into a political powerhouse. Morse was actually strengthened politically and won reelection as a Democrat in what had been a solidly Republican state.

Similarly, Republican attempts in the 1920s to purge insurgent senators — after they split with the party to back the independent progressive presidential bid of Wisconsin’s Robert M. La Follette — did serious damage to the coherence of the GOP caucus in the Senate and ushered in an era when, despite significant majorities, the party had to struggle to maintain control of the chamber.

Lieberman is neither so principled nor so politically viable as Morse or the La Follette men of the 1920s. In fact, he is arguably less viable than Chafee after the 2004 election. This is likely to be the Connecticut senator’s last term.

The question is whether he will serve it as a titular member of a Democratic caucus, which might benefit from his experience and his votes on some issues, or as a member of a Republican caucus that would be thrilled to have him.

My sense is that Democrats would be wiser to keep Lieberman in the Democratic circle for so long as he sides with the caucus on cloture votes. After all, if Al Franken prevails in the Minnesota recount and Jim Martin wins the Georgia run-off — both serious prospects — a Democratic caucus that includes Lieberman will have 59 Senate seats. And if Alaska’s Nick Begich comes from behind as that state counts the last of its ballots — a more remote prospect — a Democratic caucus that includes Lieberman will have the 60 seats needed to block a Republican filibuster.

Without Lieberman, it is tough to see how Democrats get to the filibuster-proof position that is the last piece of the puzzle of a governing majority. (It is the matter of the governing majority, not any love of Lieberman, that explains the signal from President-elect Barack Obama’s transition team that: “We’d be happy to have Sen. Lieberman caucus with the Democrats. We don’t hold any grudges.”)

If Democrats did somehow get to 60 in the Senate, and if Lieberman then betrayed the party on a critical vote, that would be the point at which to debate expelling him from the caucus.

At this point, the discussion sounds more like venting than smart, or serious, politics.