Evan Vucci/AP
President Joe Biden joins striking United Auto Workers on the picket line, in Van Buren Township, Mich. United Auto Workers President Shawn Fain stands at left.
CNN  — 

President Joe Biden on Tuesday joined members of the United Auto Workers in Michigan on the picket line, a historic moment for a modern president that comes amid a tense reelection race against a familiar foe.

The trip comes as Biden faces consistently low polling numbers on his handling of economic issues, and, back in Washington, the looming threat of a government shutdown this week. Both a prolonged strike and a shutdown could have economic consequences – something the White House is seeking to avoid as Biden tries to convince voters his economic policies are working. He’s also appearing in the battleground state of Michigan just one day before his chief political rival – whom he defeated in the 2020 presidential election – comes to the crucial swing state to make his own appeal to union workers.

Former President Donald Trump, the front-runner in the GOP presidential primary race, is scheduled to skip the second Republican debate to deliver a prime-time speech to an audience of current and former union members, including from the UAW, in Detroit on Wednesday. Trump has slammed the president for the visit, claiming Biden “had no intention” of walking the picket line until Trump said he would make a speech in Michigan.

Biden, wearing a UAW hat, spoke into a bullhorn to the workers on the picket line recounting that “the fact of the matter is that you guys, UAW, you guys saved the automobile industry” during the late 2000s and early 2010s. Biden said the companies have recovered and are doing “incredibly well” now.

“You should be doing incredibly well too,” Biden said.

Biden told the autoworkers marching that they “deserve the significant raise you need, and other benefits,” reiterating, “We saved them, it’s about time they step up for us.”

He added, “Folks, you’ve heard me say many times, Wall Street didn’t build this country, the middle class built this country, and unions built the middle class. That’s a fact, so let’s keep going. You deserve what you’ve earned, and you’ve earned a hell of a lot more than you’re getting paid.”

Biden is attempting to use the trip to support autoworkers without getting involved in the specifics of the negotiations. Amid mounting political pressure to ramp up his public support, Biden is expressing solidarity with the union members, who are striking against the Big Three automakers – General Motors, Ford and Stellantis – for a second week.

“I think the UAW gave up an incredible amount back when the automobile industry was going under,” Biden said Monday during a meeting with his HBCU advisory board when asked whether he supports the UAW’s asks in the negotiations. “They gave everything, from their pensions on. And they saved the automobile industry. And I think that now that the industry is roaring back, they should participate in the benefit of that.

“If you take a look at the significant increase in salaries for executives, growth in the industry, they should benefit from it. So, yes, I support – I’ve always supported the UAW.”

The answer was reflective of the fine line that the president is attempting to walk by standing in solidarity with striking autoworkers while not getting directly involved or putting his thumb on the scale of negotiations. The administration lacks any legal or legislative authority to act as a participant in the negotiations, but top officials, including Biden, have met with UAW leadership to discuss broader policy changes that would be seen as favorable, even as the union has criticized the administration’s support of a transition to electric vehicle manufacturing.

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Presidents, including Biden himself, previously have declined to wade into union disputes to avoid the perception of taking sides on issues in which the negotiating parties are often engaged in litigation. The National Labor Relations Board, whose members are appointed by the president but expected to function independently, has 28 pending cases that were filed by the United Auto Workers.

While Biden has repeatedly touted his status as the most pro-labor president, the UAW has yet to offer an endorsement of his reelection bid. Union members, once a reliable Democratic voting bloc, have gradually gravitated to Republican candidates, according to CNN polls and the AFL-CIO, the nation’s largest labor federation. The historic presidential picket line appearance will reaffirm his commitment to the critical voting and organizing group ahead of the 2024 election.

Biden said Tuesday that he is “not worried about that” when he was asked about the UAW not endorsing him yet.

That background of union support and the withheld endorsement has piled the pressure on Biden to do more to support the workers, but White House press secretary Karine Jean-Pierre would not explicitly say that the president backs the UAW’s specific demands.

“He is standing with the workers,” Jean-Pierre told reporters at a press briefing Monday. “We are not involved in negotiations. That is something for them to decide what is going to work for the parties that are involved, but he is standing with the autoworkers. That’s what the president is doing.”

Jean-Pierre said Biden had accepted an invitation from United Auto Workers President Shawn Fain, who will walk the picket lines with the president on Tuesday. Asked whether the visit and declarations of support for the workers meant that Biden was taking their side in negotiations, the press secretary said she was “not going to get into negotiations from here.”

“This is for the parties to negotiate,” she said. “We’re not going to speak to what’s being put at the table. What we have said over and over again is that we believe there’s an opportunity here for a win-win agreement.”

Jean-Pierre emphasized that Biden’s trip should not be seen as an endorsement of the UAW’s position in the negotiations.

“We believe this agreement can be a win-win agreement for all so but we’re not going to get into the we’re not going to litigate the specifics of the negotiations,” she repeated, pressed on where the president stood on the proposals themselves.

CNN’s MJ Lee, Kayla Tausche, Jasmine Wright and Vanessa Yurkevich contributed to this report.