DETROIT — Vice President Kamala Harris sought to shore up the support of organized labor in so-called “blue wall” states at the end of the holiday weekend, stressing that union members had a binary choice in November between her and former president Donald Trump, a candidate she said has a history of being hostile to workers.

An unconventional race that features a new name at the top of the ticket and a truncated sprint to the White House still held true to one late summer ritual: politicians making their pitch to union workers on the holiday dedicated to laborers — though Trump held no events.

Harris started the day in Michigan and then headed to Pennsylvania, where she will address steelworkers alongside President Joe Biden, their first campaign event together since he announced he was dropping out of the race and endorsing Harris. In Pittsburgh, Harris is expected to say that U.S. Steel should remain domestically owned and operated, a Harris campaign official said.

The sale of U.S. Steel to Japan-based Nippon Steel Corp. comes during political efforts to rebuild American manufacturing, and both Biden and Trump have expressed their opposition to the deal.

The effort is opposed by the United Steelworkers union, which has endorsed Harris.

In Detroit, Harris directed her fire at Trump, saying his record shows he will continue to be hostile to workers.

“As president, we will always remember Donald Trump blocked overtime benefits for millions of workers and blocked efforts to raise the minimum wage,” she said. “He appointed union busters to the National Labor Relations Board, and he supported so-called right-to-work laws.”

As she spoke, the gathered union members chanted “Trump’s a scab.”

Neither Trump nor his running mate, Sen. JD Vance of Ohio, had any advertised events on Labor Day — something the Harris campaign sought to draw attention to.

In a statement, Harris campaign spokesperson Joseph Costello said that Trump “is ditching workers on Labor Day because he is an anti-worker, anti-union extremist who will sell out working families for his billionaire donors if he takes power.”

Earlier Monday, Trump wrote posts on his social media platform, Truth Social, wishing workers a happy Labor Day and highlighting his administration’s work to bolster American workers while he was in office. He asserted that “Kamala and Biden have undone all of that.”

Harris is trying to garner the strong union support enjoyed by Biden, who has frequently described himself as the most union-friendly president in history. He was the first president to walk a picket line in 2023, and unions — including steelworkers — helped him win Pennsylvania in 2020 and will probably be vital to Harris’s chances four years later.

Harris’s campaign sought to stress that she too would be protective of American workers. The selection of Minnesota Gov. Tim Walz as her running mate was seen as reinforcing Harris’s union bona fides. Both Walz and his wife are union members, and his tenure as governor was seen as filled with pro-worker benefits.

In Michigan, Harris was boosted by another Midwestern voice, Gov. Gretchen Whitmer (D), who painted Trump, who was born wealthy and became a billionaire, as out of touch with workers and everyday Americans.

“When he was president, Donald Trump blew a $1 trillion hole in our national deficit to cut taxes for his wealthy friends and corporations,” Whitmer said. “At the same time, he gutted the job protections for union workers. He made it easier to screw people out of overtime pay and crush organizing meetings.”

“If your most famous line is ‘You’re fired,’ you sure as hell don’t understand workers,” she added.

Tyler Pager and Maegan Vazquez in Washington contributed to this report.