Joe Biden and Kamala Harris made their first joint appearance in the presidential campaign after the party convention on Monday and celebrated Labor Day with a tribute to union workers in Pittsburgh.

“We are so proud to be the most union-friendly administration in American history,” Harris said. “I love Labor Day. I love celebrating Labor Day, and Pittsburgh is the birthplace of the American labor movement.”

Between comments about the administration’s support for unions and Donald Trump’s attacks on union organizing, Vice President Harris spoke out against Nippon Steel’s impending purchase of US Steel, arguing that the famed Pennsylvania steel company should remain in the hands of American owners.

“US Steel is a long-standing American company, and it is vital to our country to maintain strong American steel companies. And I fully agree with President Biden: US Steel should remain American owned and operated.”

The United Steelworkers union, which represents about 10,000 US Steel employees, is opposed to the $14.9 billion deal, alleging that Nippon Steel violated the union’s rights to a change of control under its four-year basic collective agreement signed in 2022. The union and the companies are in arbitration negotiations.

Harris reiterated his support for the Protecting the Right to Organize (PRO) Act, a comprehensive package of labor market reforms designed to boost union organizing.

Kenny Cooper, president of the IBEW union, introduced Biden and Harris, pointing out that the passage of the Butch Lewis Act through Harris’ tie-breaking vote saved the benefits of two million union members. “They were tied up for one reason only,” he said. “We couldn’t find a Republican senator.”

Harris also cast the deciding vote for the Inflation Reduction Act, which, according to USW International President David McCall, is “revolutionizing the cement, chemical, glass and steel industries, as well as other traditional core industries.”

Donald Trump, the Republican presidential candidate, is also against the Nippon Steel deal and has announced that he would block it if he were president. Biden announced his opposition to the Nippon Steel deal in March.

Perhaps less succinctly than Harris, Biden described his administration’s successes in Pennsylvania, from clean energy investments to infrastructure money. He pointed out that his administration required project labor contracts that respected workers’ rights and demanded American products, and reminded listeners that Donald Trump appointed anti-union officials to the National Labor Relations Board.

“Wall Street did not build America,” Biden said. “The middle class built America and unions built the middle class.”

The joint appearance of Biden and Harris paints a picture of how the two might campaign in the final days before the election. Biden described Harris as someone who has “the backbone of a ramrod and the moral compass of a saint.”

Harris spent the morning in Detroit, joining union leaders at Northwestern High School touting the virtues of union organizing – the five-day work week, sick leave, vacation and other benefits.

“We celebrate unions because they helped build America and because they helped build America’s middle class,” she said. “When union wages go up, everyone’s wages go up.”

Biden will be the first sitting president to attend a UAW picket line in September 2023, supporting the union in its labor dispute with major automakers. “You guys – the UAW – saved the auto industry in 2008 and before,” Biden shouted through a megaphone on the picket line in Michigan. “You made a lot of sacrifices, gave up a lot. The companies were in trouble. Now they’re doing incredibly well, and you know what? You should be doing incredibly well, too.”

UAW President Shawn Fain is both a vocal supporter of the revival of the American labor movement and a staunch opponent of Trump. “Donald Trump is all hot air, but Kamala Harris is all action,” Fain said at the Democratic National Convention in August while wearing a T-shirt that read “Trump is a scab.” Harris supporters chanted the phrase in Detroit this morning.

Although Trump called for Fain’s “immediate firing” in his acceptance speech to the Republican National Convention, the Republican candidate has tried to win over blue-collar voters during his campaign to return to office. Renegotiating the North American Free Trade Agreement and his proposed tariffs of 10-20% on foreign trade were central to his advocacy, arguing that this would bring back manufacturing from offshore facilities.

But Project 2025 – a conservative playbook for a second Trump administration penned by the Heritage Foundation – aims to end merit-based employment for thousands of unionized federal workers. It calls for changes to “protected concerted activity” that would allow employers to more easily take action against unions and eliminate the “persuasion rule” that requires companies to disclose their data when they hire union-busting consultants.

Trump has also changed his mind in his public statements about the electric car industry. He initially called for an end to electric car regulations, but recently walked back that rhetoric after Tesla CEO Elon Musk endorsed his candidacy. During an interview on Musk’s social media platform X/Twitter, Trump raved about Musk’s handling of labor relations.

“They’re on strike,” Trump said. “I’m not going to name the company, but they’re on strike and they say, ‘That’s OK. You’re all gone. You’re all gone. So every single one of you is gone,’ and you’re the biggest.”

This prompted Teamsters President Sean O’Brien – who spoke at the RNC convention to the surprise of many union leaders – to walk back his own overtures to Trump. “Firing workers for organizing, striking and exercising their rights as Americans is economic terrorism,” O’Brien said.