Asked if he still had those views, Mr. McCain said in an e-mail message that he still believed the antiwar movement had hurt the morale of some prisoners, although he added the vast majority “performed their duty with courage and resolve irrespective of how controversy about the war influenced their view of it.”

Image John McCain arrived at Clark Air Base in the Philippines on March 14, 1973. The time he spent as a prisoner in North Vietnam helped mold his views on war policy and conduct that he discussed later in a thesis. Credit... Associated Press

Historians, though, say his assertion that the antiwar movement weakened the resistance of Americans captured late in the war is misleading, in part because almost all the most cooperative prisoners were captured early and in part because many other cultural shifts contributed to differences in the later war captives. And some of his fellow prisoners also question the connection between the war protests and the camp collaborators.

“Don’t connect those guys with the antiwar movement,” said Orson Swindle, a prisoner who became a friend of Mr. McCain. “It was the guy in the next cell who was the reason we were trying so hard to uphold the code and our honor, and those guys just betrayed everything we stood for.”

But others say it is easy to see how Mr. McCain’s dismay at prisoners’ propaganda statements could feed his current impatience with calls for a withdrawal from Iraq. In the crucible of the camps, it was easy to see the collaborators  broadcasting antiwar statements over prison loudspeakers, smiling for Jane Fonda and visiting peace activists, enjoying the rewards of better food and less torture  as embodiments of the war protesters that the North Vietnamese counted on to wear down the American war effort.

“Just like the ‘pull-out movement’ today, as I call it, the peace movement would give them something to hang their hats on,” said Richard A. Stratton, another former prisoner incarcerated with Mr. McCain. “You are being tortured and all you have to do to get them to stop is say the same thing that Bobby Kennedy is saying. The same thing that George McGovern is saying. You don’t even have to make anything up.”

Determination Redoubled

Mr. McCain, then a Navy lieutenant commander, was by all accounts what the American prisoners called a “tough resister.” He was nicknamed Crip for the severity of the injuries he sustained  a shoulder, both arms and his knee broken, with a bayonet wound near the groin  when his fighter plane was shot down in October 1967. Military rules only allowed P.O.W.’s to go home in the order of their capture, but some senior officers said his medical condition justified accepting an offer of release from the North Vietnamese. Mr. McCain, the son of a prominent admiral, did not want to be part of North Vietnamese propaganda, so he chose to endure years of torture instead.

At times, Mr. McCain seemed to court punishment, noisily cussing out his captors while giving “thumbs up” signs to his fellow prisoners. “No matter what he did, he always played to the bleachers,” Robert Coram, a military historian, wrote in a book about the camps.