As these columns went to press last night, it was still too early to call a victor in Connecticut’s Senate primary. One thing is sure despite the outcome, however: Senator Lieberman confronted more than just a hard-fought campaign. He was up against a jihad. If Mr. Lieberman is celebrating a victory this morning, it’s a sign that there is still room for moderation in the Democratic Party. But any celebration will be clouded by the vitriol, resembling a perverse kind of religious fervor, he had to overcome. The portent for the party’s future will be only more troubling if Senator Lieberman is collecting his wits this morning after a defeat. Exactly how troubling will depend on the outcome of an investigation into the fate of Mr. Lieberman’s campaign Web site.

Vigorous campaigns featuring the ugliest of rhetoric are almost as old as the Republic itself. Yet even in a nation that has witnessed the spectacle of presidential candidates accusing each other of procuring foreign mistresses or plagiarizing the Declaration of Independence, as happened in the 1800 presidential race, the Connecticut primary just concluded is something else, both for its ferocity and for its sheer personal hatred. After all, as deplorable as they were, false accusations of John Adams’s extramarital escapades at least spoke to a deeper and comprehensible fear that he embodied the aristocratic tendencies of England. Calumnies about Jefferson’s authorship of the Declaration at least were at least related to the question of whether he was suited to govern the country that Declaration had created.

To what do the attacks on Mr. Lieberman speak? As far as we can tell, to no concern more noble than anti-Semitism and racism, with a smattering of anti-Bush paranoia mixed in for taste. Just consider the rantings that have been directed at the senator in the left-wing blogosphere, as recounted by Democratic strategist Lanny Davis in yesterday’s Wall Street Journal. One commenter on the influential blog DailyKos.com wrote, “as everybody knows, jews ONLY care about the welfare of other jews; thanks ever so much for reminding everyone of this most salient fact, so that we might better ignore all that jewish propaganda [by Lieberman] about participating in the civil rights movement of the 60s and so on.” Or this: “Ned Lamont and his supporters need to [g]et real busy. Ned needs to beat Lieberman to a pulp in the debate and define what it means to be an AMerican who is NOT beholden to the Israeli Lobby.”

Even so, holding hateful opinions and acting on them are two different things. The question now is whether supporters of Mr. Lieberman’s opponent crossed that line. It certainly seems suspicious that Mr. Lieberman’s campaign Web site would crash just hours before polling, taking with it the campaign’s e-mail service including the ability to send get-out-the-vote messages to voters’ inboxes. The opponent, Ned Lamont, has denied any responsibility, but that doesn’t rule out his renegade supporters, one of whom had already attracted attention last week for circulating a caricature of Mr. Lieberman in black-face. Given that the rhetoric Mr. Lieberman’s opponents have been spewing is better suited to a Klan meeting than a senatorial primary, the senator is certainly justified in being suspicious that something more than a mere computer glitch is at work.

Time and an investigation will tell, and Mr. Lieberman has already contacted law enforcement authorities to launch an inquiry. It deserves to be pursued ruthlessly, while voters and pundits alike will be looking to the result of yesterday’s polling for an indication of where the Democratic Party is headed. Whatever that indication is, it will be hard to forget how we have come to this pass. Democrats can no longer avoid the question of whether they want to be increasingly beholden to entrepreneurs in bigotry who are purveyors of the oldest hatred and who approach politics with a perverse fervor and will stop at no dirty trick to stifle opposing points of view. Except for a few like Lanny Davis, the response of the party leaders has been decidedly lame.