A newsman pressed me a couple of days ago on the matter of the Senate election in Connecticut. Whom would I vote for? That's an improper question, as we all know: that's why voting is done in private. But I had been noisy on the subject of Joe Lieberman and could hardly, at this moment, plead the superordination of privacy. So I said, "Lieberman." And he said, Why? And I said, "I like Lieberman," and politely declined amplification.

Years ago I argued in favor of Al Lowenstein, a prominent New York liberal, for Congress, and received the same bemused interrogation from the press. On that occasion I said simply that I was defying my principled opposition to many of Lowenstein's positions in order to vote for a human being I thought superior. On the matter of Lieberman, there is more there than a personal attraction to the individual. Republican candidate Alan Schlesinger commented on my choice, "I think it's ironic that anyone as conservative as Bill Buckley would help someone as liberal as Joe Lieberman." But Schlesinger misses the point.

The important contention next Tuesday doesn't involve the Republican candidate. It is Lieberman vs. Ned Lamont, the other Democrat. And the political drama in Connecticut isn't just among the candidates. It has to do with the future of the Democratic Party -- and that future affects everyone.

What happened in this campaign was the materialization on Aug. 8 of an ideological posse. Its mission was to punish a Democrat for the sin of backing President Bush in the Iraqi war.

Now it gets a little complicated because there are many Americans who oppose the war as it has evolved. If you promise not to tell anybody, my own conviction is that if George Bush ever took to the bottle again, he might confide that he wishes he had never got into war in Iraq. I too wish he hadn't, but that's not because he was wrong in going in. He was moved by a conviction that Saddam Hussein was productively engaged in manufacturing weapons of mass destruction, that he was in league with a terrorist movement that threatened the Middle East, and that the United States needed to demonstrate its willingness to use its own resources to fight against incipient threats to regional and national security.

Joe Lieberman agreed. He was hardly the only Democrat to back Bush in 2003, but his special prominence -- he had, after all, been Al Gore's running mate in the campaign of 2000 -- attracted attention to his continued backing of Bush on foreign policy. The especially sibilant left set out to make the backing of Bush an excommunicable offense. So that when a pleasant and wealthy young man in Greenwich, Conn., volunteered to head up the posse, he got the backing of the Democratic left. And when the showdown came, the ideological avengers won the day. Lieberman was defeated in the Democratic primary.

This meant to the population at large that hard-bitten Democratic leftists were bidding for control of the party and had scored a huge victory in a critical exchange by defeating a three-term senator who once ran for vice president. The bigger they are ... the harder they fall. So there was much rejoicing in the Jacobin camp when Lieberman lost.

But of course almost immediately Lieberman announced that he would run as an independent. This gave the dissenters in Connecticut -- Democratic, Republican and independent -- an opportunity to vote against the execution of the prominent and effective incumbent, who has thought and acted in what he believed the national interest, never mind that the commander in chief was a Republican.

The features of the Democratic leadership are not yet set. The left is eager to assert itself as the true heir of the Democratic tradition, even as in 1948, under the leadership of Henry Wallace, the left attempted to take over the party of FDR and Harry Truman. It failed, and may fail again. But much depends on how much life there is in the opposition, and the first challenge is to vote to retain Joe Lieberman in office.