From the beginning of this presidential campaign, Democrat John Kerry has cited his combat experience during the Vietnam War as one of the main reasons he is prepared to become the nation's commander in chief. A group of Vietnam veterans is now challenging Senator Kerry's war record.

The group calls itself "Swift Boat Veterans For Truth," and accuses Senator Kerry of lying about his combat record in Vietnam and condemns his involvement in the anti-war movement after his return to the United States.

The veteran's group has begun running television advertisements in Ohio, West Virginia and Wisconsin, three states that are expected to be closely contested in the November election.

TV Commercial: "John Kerry has not been honest. And he lacks the capacity to lead. When the chips were down, you could not count on John Kerry. John Kerry is no war hero."

Former Navy Lieutenant Bob Elder commanded a Swift boat in Vietnam and is one of the leaders of the veterans group opposed to Senator Kerry. "We are military men," he said. "We do not think this man is qualified to be, or fit to become, the commander in chief."

The veterans group running the ad is not affiliated with President Bush's re-election campaign. A Bush-Cheney spokesman says the campaign has never, and will never question Senator Kerry's service during Vietnam.

The ad has drawn condemnation not only from the Kerry campaign, but from Republican Senator John McCain of Arizona, a former prisoner of war in Vietnam.

Senator McCain called the ad dishonest and dishonorable, and says the Bush administration should condemn the ad, as well.

The Kerry campaign says none of the 13 veterans quoted in the ad served on Senator Kerry's Swift boat during the war.

Senator Kerry's wartime service in Vietnam was highlighted during the recent Democratic National Convention in Boston. Among the featured speakers was former Army Green Beret Jim Rassman. He was rescued by John Kerry's Navy Swift boat in 1969.

Rassman: "And not just because 35 years ago John Kerry saved my life. I volunteered because I have seen John Kerry in action. I know his character. I witnessed his bravery and leadership under fire, and I know he will make a great commander in chief."

Senator Kerry's combat experience is also the focus of a new series of ads that feature his vice presidential running mate, Senator John Edwards of North Carolina.

Edwards on TV Commercial:"And if you have any question about what John Kerry is made of, just spend three minutes with the men who served with him 30 years ago who still stand by his side."

The anti-Kerry ads may have sparked a new controversy in the campaign, but most political experts contend that television ads in general have little impact on voters.

Allan Lichtman is a presidential historian at the American University here in Washington.

"There is no evidence that ads make any difference whatever in presidential elections, where voters have plenty of time to get to know the candidates and get to understand the candidates in different ways," he explained.

In another twist to the story, the Boston Globe newspaper reports that one of John Kerry's former commanding officers now believes that he made a terrible mistake in signing a statement that said Mr. Kerry did not deserve one of the medals he won for bravery in Vietnam.