It now seems apparent that President George W. Bush has made small but important gains at the expense of John Kerry since the end of the Democratic National Convention. In some measure, this brightening of the President’s position is owed to an improvement in his own approval ratings as recorded by a variety of national polls, including Gallup, which now shows Bush over the magic 50 percent approval mark for the first time in months.

It can hardly be doubted, however, that Kerry’s slide is also owed to the ferocious assault waged by the Swift Boat Veterans for Truth. This sustained attack was the first effective action taken against Kerry by an independent "527" group, after a year of attacks on Bush by liberal "527s."

It is clear that the Kerry campaign was caught off guard by the Swift Boat Veterans, and underestimated the potential impact of their efforts. Kerry undoubtedly hoped and expected that the elite media would bury the story. Despite the best efforts of the New York Times, however, the story has obtained a life of its own.

The attack has two parts, which together form a serious threat to Kerry’s position in the race. First, the Swift Boat Veterans allege that Kerry’s heroics in the Vietnam War were overstated and his wounds minor. Second, they insist on reminding voters of Kerry’s scurrilous conduct after he returned from service, when he devoted his energy to serving as a font of sound-bites for the North Vietnamese propaganda machine.

Taken by themselves, these allegations would not seem on their face to be enough to derail a presidential campaign, at least in recent times. War stories are notoriously difficult to pin down with precision, and Kerry’s conduct after his short tour of duty was not noticeably worse than the anti-war agitation of Bill Clinton, who dodged the draft and organized protests while on foreign soil. So why have the charges taken a toll?

The answer is simple. Every presidential campaign relies on a mixture of biography (appealing parts of the life story of the candidate), political record (appealing aspects of the candidate’s prior service in office), and issues (appealing stands on key controversies of the day). To a greater extent than any major party presidential candidate since Dwight D. Eisenhower, John Kerry has staked almost everything on biography.

Kerry is not running on his record in the Senate, which is both qualitatively undistinguished and far to the left of the American mainstream. Indeed, one is hard pressed to hear any admission by Kerry that he has ever served in the Senate. Though he makes noises about certain issues, he is not really running on issues, either, for the obvious reason that his positions on several key issues (Iraq, for example, or gay marriage) are so tied up in "nuances" and reversals that they do not meet the minimum threshold of coherence necessary to serve as the central thrust of a campaign. In these areas, Kerry’s objective is damage limitation.

It is in the area of biography that Kerry has placed his claim on the presidency. Specifically, he won the Democratic nomination and has offered himself to the American people in the general election on the basis of his military service in Vietnam. Anything that undermines his claims in that area poses a mortal threat to his candidacy. In contrast, Bill Clinton could survive Vietnam-era indiscretions because his campaign was much more balanced, and indeed focused on record and issues above biography. To the extent that biography entered into his campaign, it was the story of the rise of a bright young man from hardship, a story that could not easily be dented by any revelations, Vietnam or otherwise.

The thrust of the first Swift Boat Veterans’ attack brought into question whether Kerry’s self-image from Vietnam was accurate. While still caught in the fog of war, the charges and counter-charges have yielded two certain facts. First, Kerry was not in Cambodia as he has repeatedly claimed for political purposes (once saying the experience was "seared" in his memory), a revelation that cannot help but throw a question around other Kerry claims. Second, the group of swift boat veterans who support him is much smaller than the group that opposes him. For Kerry to be hurt, undecided voters do not have to conclude with certainty that he is lying; they only have to conclude that his record is in doubt. They will then set aside that rationale for a Kerry presidency and move on to other considerations. Unfortunately for Kerry, he has developed no other compelling rationale.

The second line of attack stands on its own, and does not depend on the first. Indeed, one could concede that Kerry’s version of his Vietnam service was entirely correct and still turn against him on the basis of his later activity. After all, whether one is a war hero might be said to depend on the overall degree to which one contributed to the military cause of one’s country. We do not call Benedict Arnold a war hero, even though he led the charge that broke the British at Saratoga. His subsequent betrayal negates Saratoga, as Kerry’s subsequent behavior leaves open the question of whether he cost more lives—American and Vietnamese—out of uniform than he saved while in uniform. To the extent that his actions contributed to the victory of Stalinism in Indochina, it is obtuse to consider him a "war hero" in any meaningful sense.

Because there is a solid 45 percent anti-Bush vote, there is a limit to how low Kerry will go as a result of this bleeding. But his campaign cannot be encouraged. Bush is now set up for his convention. Even a very small "bounce"—and one should not expect a large one—could put Bush 5 points ahead. How Kerry will make it up, unless aided by untoward events, is hard to say.

Andrew E. Busch is a Professor of Government at Claremont McKenna College and an Adjunct Fellow of the Ashbrook Center.