Republicans backing the Trump campaign have kept up their attacks on the military career of Gov. Tim Walz of Minnesota during the Democratic convention, accusing him, among other things, of having abandoned his fellow soldiers by retiring from the National Guard to run for Congress in 2006, months before his unit deployed to Iraq.

But the attack may not be having the intended effect. Many veterans, including undecided and conservative voters, said this week that they saw the sniping over Mr. Walz’s service as harmful to all veterans, in and out of the political arena.

The recent attacks on Mr. Walz, the Democratic nominee for vice president, were begun by his opponent on the Republican ticket, Senator JD Vance of Ohio, who served in the Marine Corps for four years. And they have been repeated by other prominent Republicans who are veterans, including 50 members of Congress who signed a letter this week claiming that Mr. Walz had lied and had “violated the trust” of other veterans.

“Name-calling, talking about people’s record, like, that’s not helpful,” said Vince Young, 32, a former Marine Corps mortarman and undecided voter who lives in Charlotte, N.C. He said his main concern was the economy, and that seeing one veteran disparaging another turned him off.

“I think it’s not really beneficial to anyone,” he said. “I want to hear, what are you going to do?”

Some Democrats have responded with negative comments about Mr. Vance’s military record, but that doesn’t sit well with many veterans, either.

“It’s frustrating to see both candidates belittle one another’s service,” said Elizabeth Hartman, 33, the commander of an American Legion post in New Bern, N.C., and a former Arabic linguist in the Marine Corps who considers herself a conservative. “Because at the end of the day, both candidates did something that less than 1 percent of the population will ever have the courage to do.”

Like Mr. Young, Ms. Hartman said she wanted the candidates to focus on current issues, like immigration, instead.

The attacks on Mr. Walz’s military record were reminiscent of those during the 2004 presidential campaign, when a well-funded political group aligned with Republicans hit the Democratic presidential nominee, John Kerry, with allegations — most of them unfounded — that he had lied about his service in the Vietnam War. Many political commentators said the attacks helped his opponent, George W. Bush, win a narrow victory.

It is unclear whether the same strategy would work in 2024, said Matt Gallagher, 41, a former Army captain who commanded a scout platoon during the 2007 troop surge in Iraq and is now a writer in residence at the Air Force Academy in Colorado Springs.

“In 2004, Republicans were able to reopen the wound of Vietnam, which had been such a huge, divisive issue for America,” Mr. Gallagher said. “But Iraq and Afghanistan are not Vietnam. People didn’t really care about them, even when they were happening, and I’m not sure they’ll care now.”

Beginning with George Washington, Americans have historically been eager to elect battlefield heroes to high office. For generations, nearly every conflict produced at least one president: Andrew Jackson, Zachary Taylor, Ulysses S. Grant, Theodore Roosevelt, Dwight D. Eisenhower.

But the pattern faltered after the Vietnam War split the nation. The commander in Vietnam, Gen. William C. Westmoreland, lost a bid to become governor of South Carolina in 1974, and in the decades since then, every Vietnam veteran who has vied for the White House has fallen short.

Today, trying to reprise the grievances and political divisions of a past war may be a mistake, Mr. Gallagher said.

“It will matter to some people,” he said. “But so many people are disconnected from the military now that this feels like a transitional moment in American politics, where fighting over what you did in the war doesn’t really matter that much.”

Veterans are by no means a uniform voting bloc; their opinions and political allegiances vary about as widely as those of the rest of the population. Because their numbers skew heavily male and somewhat older than nonveteran adults, they tend to lean conservative as a group, but younger vets and serving troops are far more diverse, and more evenly divided on party lines. And in all cases, surveys suggest, veterans tend to be more civically engaged than average.

To be sure, there are numerous veterans who have seized on Republicans’ portrayals of Mr. Walz’s record as evidence of poor character. But many of them had probably already made up their minds not to vote for the Democrats, said Paul Rieckhoff, 49, who deployed to Iraq as an infantry officer and recently founded the political advocacy group Independent Veterans of America.

Still, he said, in a tight race, swaying even a few undecided voters could make a difference.

“Military service is a great talking point for campaigns, because it carries a lot of emotional weight, but civilians don’t really understand it,” Mr. Rieckhoff said.

He pointed out that the meaning of specific details of a candidate’s military career — like Mr. Walz serving as a command sergeant major, but not retiring as one, or Mr. Vance deploying as a Marine but serving in a noncombat job — can be lost on ordinary voters.

“Because the nuance is lost, they can use military service as a proxy for all sorts of values,” he said of political strategists in both parties. “They can make someone seem like a coward or a hero. A lot of it is misinformation, but in the current political atmosphere, misinformation works.”

Mr. Rieckhoff said he thought the criticism of Mr. Walz was unfounded, and that Mr. Walz probably achieved more for troops and veterans by serving in Congress — where he championed education and mental health resources for veterans — than one sergeant major could have on a deployment in Iraq.

So far, the Harris-Walz campaign has not mounted comparable attacks on Mr. Vance’s military career. In a speech, Mr. Walz said, “To anyone brave enough to put on that uniform for our great country, including my opponent, I just have a few simple words: Thank you for your service and sacrifice.”

Several veterans said they were glad to see both major parties choose nominees who had served.

Lt. Mike Auten, 31, a former Marine now serving in the Navy Reserve and studying medicine in New York City, called that a win for civilian-military relations. “It poses an opportunity,” he said, “for people to engage critically with what it means to be in the military, with the variety of roles in the military, with the variety of experiences.”