The United Auto Workers endorsed President Joe Biden for reelection on Wednesday, putting a high-profile union behind the Democrat’s 2024 campaign.

Shawn Fain, the union’s president, announced the UAW’s backing during the union’s convention in Washington, D.C. He said in a speech to members that Biden would give workers “the best shot” at organizing, winning strong union contracts and fighting “the billionaire class.”

He also took several swipes at former President Donald Trump, the likely GOP nominee.

“This November, we can stand up and elect someone who stands with us… or we can elect someone who will divide us and fight us every step of the way,” Fain said.

The UAW is coming off a historic and successful six-week strike against the “Big 3” automakers, Ford, General Motors and Jeep parent company Stellantis. Biden took the highly unusual step of visiting a picket line in Michigan to show his support for the strikers as a sitting president.

Fain compared Biden to Trump, who did not publicly support General Motors workers during their 2019 strike when he was president.

He went on to call Trump “a scab.”

“Rarely as a union do you get so clearly a choice between two candidates.”

Biden delivered a speech after Fain, playing up his pro-labor record and promising to fight for unions in a second term. The longtime labor ally has declared himself “the most pro-union” president in history and stood by that description on Wednesday.

“The middle class built America, and America built the middle class,” Biden said. “I’m honored to have your back and you have mine.”

The UAW also endorsed Biden during his 2020 run against then-President Donald Trump. The former president is leading far ahead in polls to grab the GOP nomination once again, though former South Carolina Gov. Nikki Haley remains in the race as his lone surviving challenger.

Most unions throw their political weight — and election ground-game operations — behind Democrats like Biden. Although Trump continues to court blue-collar voters and styles himself the candidate for the working class, his record as president was overwhelmingly hostile to unions and their efforts to organize more workers.

Union endorsements typically play a much larger role in years with contested Democratic primaries, where candidates are vying for organized labor’s support. Most unions are expected to come out and endorse Biden regardless of who the GOP nominee turns out to be; the main question is when they will publicly announce their backing.

The UAW’s support is particularly helpful in the union’s home state of Michigan, a crucial battleground that narrowly went for Biden in 2020. Though once part of Democrats’ “blue wall,” Michigan went for Trump in 2016 — the first time a Republican nabbed the state’s electors in 28 years.