In the more than 150 years since workers first formed labor unions in the United States, no American president has ever stood “in solidarity” with workers on a picket line. Joe Biden has vowed to do exactly that with striking autoworkers in Michigan on Tuesday.

“This is genuinely new – I don’t think it’s ever happened before, a president on a picket line,” said Nelson Lichtenstein, a longtime labor historian at the University of California, Santa Barbara. “Candidates do it frequently and prominent senators, but not a president.”

Biden’s visit to the picket line, labor experts say, will give him a political boost in Michigan and other industrial swing states and might also help nudge the United Auto Workers (UAW) and automakers to a quicker settlement. But some experts say his visit could backfire if the walkout drags on for months or seriously hurts the nation’s economy.

Biden’s predecessors were often far more hostile toward strikers. In 1894, Grover Cleveland dispatched federal troops to help shut down a railroad strike; during the Korean war in 1952, Harry Truman seized the nation’s steel mills in response to a steelworkers’ strike; and in 1981, Ronald Reagan fired 11,345 striking air traffic controllers.

“Biden has said he will be the most pro-union president ever, and visiting a picket line is indeed unprecedented for a president,” said Meg Jacobs, a labor historian at Princeton University.

The UAW strike is the first to hit all three big US car manufacturers simultaneously. The union has emphasized the huge profits Ford, General Motors and Stellantis have made since the 2008/2009 recession and claimed little has been passed on to workers.

CEO pay at the big three has increased by 40% since 2013 as profits have soared. GM’s Mary Barra, the highest-paid CEO of the three, pocketed $28.97m last year. Meanwhile, auto manufacturing workers have seen their average real hourly earnings fall 19.3% since 2008.

The union’s messaging has so far won popular support, with 58% of Americans backing the strike according to a Reuters/Ipsos poll.

On Friday, the UAW’s president, Shawn Fain, called for everyone “from our friends and families all the way up to the president of the United States” to “join us on the picket line”. Hours later, Biden tweeted, “Tuesday, I’ll go to Michigan to join the picket line,” saying he planned to “stand in solidarity with the men and women” of the UAW.

Jacobs said the picket line visit could have important political benefits for Biden. “It’s a smart move. There’s no way for him to win the presidency without industrial states like Michigan,” Jacobs said. “Biden has to do well in the important industrial swing states that Hillary Clinton lost to Donald Trump in 2016 [Michigan, Wisconsin and Pennsylvania – all of which Biden won back in 2020]. Going to the picket line signals a commitment to working families, to the working class. It signals to workers in those states that he is authentic about this.”

On Friday, the Trump campaign attacked Biden’s plan to join the UAW strikers, calling it “nothing more than a cheap photo-op” and saying it was inspired by Trump’s plan to speak in Detroit to union members on Wednesday. A week ago, Trump campaign sources said the former president would give a speech to 500 workers, including many UAW members, on 27 September at the same time the second Republican presidential debate is held. Labor experts said it was highly unusual for a former president to arrive in a city that’s the center of a major strike with the intention of somehow intervening and making political gains. Trump is expected to attack Biden over his plan to bring about a quick transition to electric vehicles, a move that Trump says will endanger autoworkers’ jobs.

All this shows that Biden and Trump are vying for an important political group, blue-collar workers, and that helps explain Biden’s visit. “Biden realizes that constituency is important,” Jacobs said.

Marick Masters, an auto industry expert at Wayne State University in Detroit, said Biden’s plan to join a picket line was an astute way to counter Trump’s Detroit speech. “In his visit, Trump is trying to energize his base and embarrass Biden,” Masters said. “But Biden coming to a picket line here will make it harder for Trump to embarrass Biden.”

Masters said there was an easy way for Biden to trump his predecessor, who hasn’t indicated that he would join a picket line: “All Biden has to say is ‘I came and stood by you. Someone else who occupied this office didn’t.’”

Masters agreed that Biden’s visit could give him a needed political boost. “A lot of autoworkers are blase when it comes to Biden. He doesn’t get a great deal of enthusiasm. But his visit could generate support,” Masters said. “[Union members] will go the extra mile and be more willing to campaign for him and vote for him. It could very well make the difference” in the industrial swing states “if there is a close election and it’s a redo of 2020.”

Biden’s visit could still backfire, said Masters, if the strike drags on for months or is seen as pushing the nation into recession. But if it doesn’t: “I think this show of commitment will inspire a lot of union members and they won’t forget this,” he said.

Some labor experts see Biden’s visit as mainly symbolic as far as the contract talks are concerned. They say that notwithstanding his pro-union rhetoric, he doesn’t have much leverage.

Art Wheaton, director of labor studies at Cornell University, said he wasn’t sure whether Biden’s visit would help speed a settlement, but he didn’t doubt that it would help him politically. “I don’t know if it persuades GM [or the other automakers] to move faster,” Wheaton said.

As for the political angle, Wheaton said: “He’s going to be on the union side, saying, ‘I’m for the working person, I’m publicly siding with the UAW.’ It takes away one talking point from Trump that Biden’s not doing anything. Biden’s standing up with the workers.”

While Biden’s move may be unprecedented, Princeton’s Jacobs said she still saw Franklin Roosevelt as the most pro-union president in history. “I think FDR deserves the title as the most friendly toward labor,” Jacobs said. “Without the Wagner Act [the landmark 1935 law that the New Deal Congress enacted to create a federally guaranteed right to unionize and bargain collectively], we wouldn’t have the UAW and the labor protections we have today. I think Biden is very much a New Deal Democrat. He sees labor in the same way. It’s not new that he talks about corporations’ record profits and translating record profits into record gains for workers.”

If ever there was a moment for a Democratic president to join a picket line, this is probably it, said UC Santa Barbara’s Lichtenstein. “Today the Democratic party is probably more united on labor issues than any time since the New Deal, and even then, the whole southern Democratic contingent was hostile toward labor,” he said. “Even with Kennedy and Johnson, there was a whole anti-labor contingent in the Democratic party. But right now is a rare moment when labor is very popular, and it usually isn’t.”