As we watch the left of the Democratic Party pressing its case to return to the top of the heap in American politics, or at least evade the fate of the Dodo, we have ever more evidence validating an insight on which I stake my reputation as a political seer. To wit: Partisan politics more often falls under the professional expertise of the psychiatrist than that of the political scientist. A learned shrink can often tell us more about a political issue than any other professional.

Consider the ongoing controversy over Senator Jean-Francois Kerry’s military service in the faraway Vietnam War. You doubt that the controversy is ongoing? Just last Sunday a front-page story in the New York Times reported that some of Senator Kerry’s supporters during his ill-fated 2004 presidential campaign are endeavoring to prove him a war hero with an unblemished record of heroism. Their targets are the Swift Boat Veterans for Truth. These Swifties, as they are called, are the Vietnam vets who claimed that when they served with Mr. Kerry they found him to be a self-aggrandizing, self-indulgent showoff. All insist he exaggerated his feats of heroism, and some testify that he lied about his wounds and heroics. Many American voters were persuaded.

Now why is this debate being launched? Any innocent observer who watched the showboating senator from Massachusetts bungle his 2004 presidential campaign must know that he is today a self-aggrandizing, self-indulgent showoff. Why would he not have been one as a youth, back in the late 1960s when he brought camera equipment into the jungles to film himself at war? After an early exit from military service, he proceeded to follow the fashion of the times and oppose the war, appearing before a Senate committee in 1971 to accuse the American military of systematically committing war crimes. Then just over three decades later this strange man chose to make his Vietnam experience a major theme of his presidential candidacy. This is a matter for a seasoned psychiatrist to explain. To the rest of us it appears as egotism at the outer reaches of sanity.

Yet this attack on the Swift Boat Veterans is not contained to Mr. Kerry’s supporters. The senator himself has been obsessive about the Swifties since their ads against him did his campaign so much damage. As David Holman reported in the May issue of The American Spectator, “A year and a half after he lost the 2004 presidential election John Kerry can’t get enough of the Swift Boat Veterans for Truth. No matter the occasion, he [Kerry] doesn’t miss an opportunity to parade his campaign wounds however incoherently and obsessively.”

Mr. Kerry has complained of the “Swift Boat-style Republican attack ads” in fundraising appeals on behalf of other candidates. He invoked the Swifties in opposing the Supreme Court nomination of Judge Samuel Alito. When asked if he had received contributions from the disgraced Washington lobbyist, Jack Abramoff, Mr. Kerry snapped, “That’s another of their Swift Boat-style tactics where they throw up the mud and stick it.” Mr. Holman reports that Mr. Kerry has resorted to these slurs on the Swifties in eight other fundraising appeals. Moreover, in the asylum that is the Democratic Party’s angry left, “Swift Boat” has become a verb and an adjective. The left-wing magazine Mother Jones writes of the Bush administration “Swiftboating their enemies.” Senator Hillary Rodham Clinton admonishes against the dread Republicans’ employment of “swift boat tactics.” In the Kultursmog’s parlance of hate terms, Swiftboat is about to join such terms as McCarthyism and McCarthyite.

Now we read that the campaign against the Swifties is going to gain momentum. The sorehead Kerry supporters have joined together in a group called the Patriot Project. It will seek out the Swifties and scrutinize their complaints against Mr. Kerry. It will also support opponents of the war in Iraq and visit editorial offices to make the case for such veterans as the Honorable John P. Murtha, a Vietnam War vet who now opposes the Iraq War. All of this sounds like political harassment to me, but as the shrinks are wont to say, “If it is true for you, it is true for you.” For a certitude, the left wing of the Democratic Party believes that whatever it believes is true. Mr. Kerry believes he would be president today if he had not been swiftboated. He has hired a researcher to prove from naval archives that he was in Cambodia three decades ago for a few hours when the Nixon administration said he was not supposed to be there. What does this prove? I think it proves that beyond being a self-aggrandizing, self-indulgent showoff, this guy is a nut. Yet I leave all this to the professionals.

Mr. Tyrrell is the founder and editor in chief of The American Spectator, a contributing editor to The New York Sun, and an adjunct scholar at the Hudson Institute.