The two men railed against Donald Trump and urged voters to return their ballots early, as polls show a close race in the state.
Gov. Tim Walz of Minnesota raced across battleground Wisconsin on Tuesday, exhorting voters to get to the polls on the state’s first day of early voting and just two weeks before Election Day.
At a rally in Madison, Mr. Walz appeared alongside former President Barack Obama for the first time on the campaign trail, giving Mr. Obama a bro hug onstage. The two took turns, in successive speeches, laying into former President Donald J. Trump and stressing the urgency of the moment to vote for Vice President Kamala Harris, who leads the Democratic presidential ticket with Mr. Walz.
“Our team is running like everything is on the line, because everything’s on the line,” Mr. Walz told the crowd of thousands at an event center. He urged voters to avoid complacency, suggesting that a second term for Mr. Trump would be even more chaotic than the first and that he was “far more dangerous” now.
“He is not the 2016 Donald Trump — this is a brand-new version,” Mr. Walz said. “The consequences of putting him back into office are deadly serious.”
In Racine on Tuesday night, he addressed comments from John Kelly, a former Trump chief of staff, who said recently that Mr. Trump had told him during his presidency that he wished he had generals like Adolf Hitler’s. “As a 24-year veteran of our military, that makes me sick as hell,” Mr. Walz said. “The guardrails are gone. Trump is descending into this madness.”
In Madison, Mr. Obama was lighthearted as he began, making jokes and telling the audience that Mr. Walz was “the kind of person who should be in politics.”
But his wisecracks grew pointed when discussing his successor, whom both men tried to paint as out of touch with ordinary voters.
“Do you think Donald Trump ever changed a diaper?” Mr. Obama asked, as the crowd laughed and shouted. “He’d be like: ‘Jeeves! Jeeves, change that diaper.’ He’d have somebody else do it.”
Democrats have made questions over Mr. Trump’s age, his stamina and his competence a part of their closing argument, especially as Mr. Trump has appeared tired on the trail and meandered frequently in speeches.
Mr. Walz said Mr. Trump “does not have stamina,” while Mr. Obama mocked what he said were speeches more akin to “word salads.”
“You’d be worried if Grandpa was acting like this,” he said.
And Mr. Walz found easy fodder in Mr. Trump’s recent appearance at a McDonald’s in suburban Philadelphia, where the former president briefly worked the fryer and handed food to preselected customers through the drive-through window. With glee, he attacked the stop as a naked political stunt, joked that Mr. Trump had dressed up as an employee because he mistakenly thought it was Halloween and compared him to Ronald McDonald, the clown that is the fast-food chain’s mascot.
“There is something not just nuts, but cruel, about a billionaire using people’s livelihoods as a political prop,” Mr. Walz said. Mr. Trump’s economic agenda, he added, “diminishes those very workers that he was cosplaying as.”
Both men instructed voters to return their ballots early, as Republicans have shown an unusual strength in the initial days of early voting around the country.
“If you haven’t voted yet, I won’t be offended if you just walk out right now — go vote,” Mr. Obama said, adding that he had voted on Monday in Chicago, dropping his ballot off in a mailbox.
In Wisconsin, where polls have consistently shown a tight race between Mr. Trump and Ms. Harris, Mr. Walz leapfrogged from one Democratic stronghold to another, flying over the stretch of rural farm country where Trump-Vance signs dotted the autumn foliage to Milwaukee before rallying in Racine, at the edge of Lake Michigan.
Addressing a smaller crowd at a memorial hall in Racine at the end of a long day of campaigning, Mr. Walz spoke more quickly, and in a more staccato manner. At one point, he summed up one of his main arguments — that Republicans meddle too much in education policy, health care and abortion rights, and that the world works better when everyone minds their own business.
“Just leave us the hell alone,” he said.