LOS ANGELES — Minnesota Gov. Tim Walz pushed back on GOP attacks on his military service and the timing of his departure from the Army National Guard during his first solo campaign appearance a week after being named Vice President Kamala Harris’s running mate.

During a speech Tuesday before one of the nation’s largest public sector unions, the longtime National Guard member took a moment to address recent scrutiny of his military record by former president Donald Trump and his allies, including his running mate Sen. JD Vance (R-Ohio).

“I firmly believe you should never degenerate another person’s service record,” Walz said at the convention of the American Federation of State, County and Municipal Employees (AFSCME). “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.”

Walz served for more than two decades in the Army National Guard and his military service was likely viewed as an asset by Harris when she chose Walz as her running mate. But at least three of Walz’s former Guard colleagues have publicly voiced disappointment about his decision to leave the service when the unit was preparing to go to war in Iraq. Walz ultimately chose to leave the guard in 2005 to run for Congress and won a House seat the following year.

On Tuesday, Walz noted that he signed up for the Army National Guard two days after his 17th birthday with encouragement from his father, who served in the Army during the Korean War, and he said he did so because of his love for his country.

“In 2005, I felt the call of duty again, this time giving service to my country in the halls of Congress,” Walz said on Tuesday. “My students inspired me to run for that office, and I was proud to make it to Washington. I was a member of the Veterans Affairs Committee and a champion of our men and women in uniform. I’m going to say it again as clearly as I can, I am damn proud of my service to this country.”

The Trump campaign has tried to capitalize on the controversy over the timing of Walz’s retirement. And Trump allies have also focused fresh scrutiny of Walz’s comments during a 2018 gubernatorial campaign event where he stated “we can make sure those weapons of war that I carried in war” are not on America’s streets. A campaign spokesman acknowledged Friday that Walz “misspoke” during the 2018 exchange.

Walz did not serve in combat, according to the Minnesota Army National Guard. Vance, who is also a veteran, has specifically drawn attention to that 2018 comment: “When were you ever in a war?” Vance said at a recent campaign event in Michigan in comments directed to Walz.

After Walz said that he would never denigrate the service of a fellow veteran, Vance responded to him on X, the social media platform formerly known as Twitter.

“Hi Tim, I thank you for your service,” Vance wrote. “But you shouldn’t have lied about it. You shouldn’t have said you went to war when you didn’t. Nor should you have said that you didn’t know your unit was going to Iraq. Happy to discuss more in a debate.”

The Minnesota Governor’s address to AFSCME, that otherwise largely focused on how Democratic policies would benefit working class voters, underscored the fierce battle for the loyalty of blue-collar voters that is underway between Harris and Trump.

Before President Biden announced that he was withdrawing from the presidential race this summer, some polls suggested that support for the Democratic ticket was softening among working-class voters. On the campaign trail, Trump had repeatedly faulted Biden for the rise in prices due to inflation.

Trump has also strategically courted key labor leaders as he has attempted to drive a wedge between union leaders and rank-and-file members, who he has argued should be more receptive to his candidacy. He attended a meeting with the Teamster union in January and Teamsters President Sean O’Brien was one of the featured speakers at the Republican National Convention, though he did not endorse Trump.

As Harris and Walz try to solidify their relationship with organized labor in this new phase of the campaign, Harris unveiled a proposal last week to raise the minimum wage and eliminate taxes on tips for service and hospitality workers. Trump first proposed eliminating taxes on tips in June during a rally in Las Vegas.

Walz offered harsh criticism of the records of both Trump and Vance on Tuesday, arguing that they would “wage war on workers” if they are elected in November. Walz, a former teacher and football coach, highlighted his own union membership in his remarks, telling the crowd as he opened his remarks that he was “the first union member on a presidential ticket since Ronald Reagan.” (Trump was a member of the Screen Actors Guild — American Federation of Television and Radio Artists but resigned after leaders considered removing him for his role in the Jan. 6, 2021, attack on the U.S. Capitol.)

Walz questioned whether Vance “was a value add to this campaign or not” and mocked Trump’s work ethic — asking the boisterous and receptive audience to imagine whether Trump would make it as a worker at McDonald’s.

“Can you simply picture Donald Trump working at a McDonald’s, trying to make a McFlurry or something?” Walz asked. “He couldn’t run that damn McFlurry machine if it cost him anything.”

He later said Vance “has never cast a vote on a pro-worker bill in his life.”

“The only thing those two guys know about working people is how to work to take advantage of them,” Walz said.