An aide pointed out that in a different appearance this year, Mr. Blumenthal was forthright about not having gone to war. In a Senate debate in March, he responded to a question about Iran and the use of military force by saying, “Although I did not serve in Vietnam, I have seen firsthand the effects of military action, and no one wants it to be the first resort, nor do we want to mortgage the country’s future with a deficit that is ballooning out of control.”

On a less serious matter, another flattering but untrue description of Mr. Blumenthal’s history has appeared in profiles about him. In two largely favorable profiles, the Slate article and a magazine article in The Hartford Courant in 2004 with which he cooperated, Mr. Blumenthal is described prominently as having served as captain of the swim team at Harvard. Records at the college show that he was never on the team.

Mr. Blumenthal said he did not provide the information to reporters, was unsure how it got into circulation and was “astonished” when he saw it in print.

Mr. Blumenthal has made veterans’ issues a centerpiece of his public life and his Senate campaign, but even those who have worked closely with him have gotten the misimpression that he served in Vietnam.

In an interview, Jean Risley, the chairwoman of the Connecticut Vietnam Veterans Memorial Inc., recalled listening to an emotional Mr. Blumenthal offering remarks at the dedication of the memorial. She remembered him describing the indignities that he and other veterans faced when they returned from Vietnam.

“It was a sad moment,” she recalled. “He said, ‘When we came back, we were spat on; we couldn’t wear our uniforms.’ It looked like he was sad to me when he said it.”

Ms. Risley later telephoned the reporter to say she had checked into Mr. Blumenthal’s military background and learned that he had not, in fact, served in Vietnam.