Nobody picked on his Rosa Parks biography. Who would pick on Rosa Parks? Or sneered at his works on Jimmy Carter or Henry Ford.

But a few weeks before the Iowa caucuses, historian Douglas Brinkley published his eighth book,"Tour of Duty," an exploration of how Vietnam shaped Sen. John Kerry. A vet named Jim Rassmann, a Republican, thumbed through it in an Oregon bookstore, found the part that told how Kerry had saved his life, plucking him from enemy waters, bullets whizzing around them, and nearly burst into tears, right there in the Barnes & Noble. The drama! The reaction for which an author prays! Rassmann, who had had no contact with Kerry since that day in 1969, called the campaign, volunteered to help, and flew to Des Moines.

With Rassmann beside him throughout the primaries and the convention, Kerry made his battlefield leadership and the camaraderie of servicemen the central theme of his campaign. Brinkley's book, drawn primarily from Kerry's extensive journals and letters from the period, depicts a young naval officer who displayed unflinching courage, even as he agonized over the war's morality. But his admiring recounting of the Massachusetts senator's war record also helped lead to the current guns of August.

For the past three weeks, the dominant issue of the presidential race has been not the war we are in now, but the war of 35 years ago. A group called Swift Boat Veterans for Truth has been running television ads accusing Kerry of inflating or lying about his war record. Several of the men in that group said"Tour of Duty" enraged them and prompted their campaign. A best-selling book about their recollections,"Unfit for Command," tries to refute Brinkley's conclusions, charging Kerry with calculation and cowardice during his four months in battle.

The escalating attacks and counter-attacks find Brinkley, a 43-year-old presidential scholar at the University of New Orleans, trying to avoid collateral damage.

His cell phone is too full to receive any more messages. Reporters, sometimes four from one newspaper, call him hourly, demanding help in sorting fact from fabrication. The vets against Kerry go on cable TV and mischaracterize his work, he says. His knee needs surgery from too much running, his baby needs rocking, boxes in his new house need unpacking. His book editor needs his next manuscript. His New Yorker editor needs his next article. And NBC needs him to stop thinking like an academic and start talking like a pundit when it puts him on camera during next week's Republican National Convention.

All this public busyness, and Brinkley's eagerness to expand it, has brought some sniping: Other historians in the notoriously snobbish world of academia sniff -- with a"please don't attribute this to me, of course" -- that Brinkley is a"popular" historian, so voracious for media attention that he lacks the rigor to make significant contributions to scholarship. So he is paying a price for the notoriety of this book, but also reaping a benefit."Tour of Duty" has sold 95,000 copies so far, making it Brinkley's first bestseller. The paperback, with a new introduction, comes out next month.

Amiable and driven, he has maintained a frenzied pace for years. But when the nuance of history collides with the sloganeering of the political present,"this is a whole different world," Brinkley said in an interview this week."I compartmentalize. I try not to deal with the Swift boat wars until mid-afternoon. It's unpleasant. I feel frustrated."

The effort to discredit Kerry's war heroism is"an outrage," said Brinkley."There is just no evidence that John Kerry did not win his medals properly. It's a smear campaign, just as Democrats smeared Bush back in the spring" regarding his service in the Texas Air National Guard."I treasure facts. When you have facts being distorted for a political agenda, I mind."

The Kerry campaign has refused to release Kerry's personal Vietnam archive, including his journals and letters, saying that the senator is contractually bound to grant Brinkley exclusive access to the material. But Brinkley said this week the papers are the property of the senator and in his full control.

"I don't mind if John Kerry shows anybody anything," he said."If he wants to let anybody in, that's his business. Go bug John Kerry, and leave me alone." The exclusivity agreement, he said, simply requires"that anybody quoting any of the material needs to cite my book."

Brinkley has made corrections and revisions to the paperback version, he said, but most of those are minor, spelling errors and the like. A new introduction includes a fuller version of the Rassmann story; Brinkley said that Kerry couldn't recall the spelling of Rassmann's last name during their interviews, and the historian was unable to locate the Green Beret before his deadline. He also said he was unable to locate and interview Stephen Gardner, the lone member of Kerry's Swift boat crew who claims that the senator lied about his combat experience.

Kerry repeatedly said in the past that he was ordered illegally into Cambodia during Christmas 1968. His detractors claim he never entered that country at all. In"Tour of Duty," Brinkley does not place Kerry in Cambodia but, quoting from Kerry's journal, notes that Kerry's Swift boat was"patrolling near the Cambodian line." Later in the book, Brinkley writes that Kerry and his fellow Swift boat operators"went on dropping Navy SEALS off along the Cambodian border."

"I'm under the impression that they were near the Cambodian border," said Brinkley, in the interview. So Kerry's statement about being in Cambodia at Christmas"is obviously wrong," he said."It's a mongrel phrase he should never have uttered. I stick to my story."...