With more than 1.3 million members, the Teamsters International union is one of the 10 largest labor unions in the country.
And the Teamsters are the only one of the nation's top 10 labor unions not to endorse Vice President Kamala Harris in the 2024 presidential election.
Democratic presidential nominee Harris is seeking to maintain her party's traditionally strong support from labor unions while taking on former President Trump, and will make an appeal to the National Labor Party on Monday.
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Vice President Kamala Harris speaks during a campaign rally at Bojangles' Coliseum, Thursday, Sept. 12, 2024, in Charlotte, North Carolina. (AP Photo/Jacqueline Martin)
Teamsters President Sean O'Brien late last year announced the union's first-ever interview process for 2024 presidential endorsements, inviting candidates from both major parties to make their case.
The Teamsters met with President Trump earlier this year and also met separately with President Biden, whose presidency saw Harris take over as head of the Democratic National Convention two months ago.
WATCH: What the Teamsters president told Fox News about not being invited to speak at the Democratic Convention
“I look forward to discussing the direction of the country and the issues that are important to working people,” O'Brien said earlier this month, with Harris in mind.
O'Brien made history in July when he became the first Teamsters chairman to speak at the Republican National Convention.
Sean O'Brien, executive director of the International Brotherhood of Teamsters, speaks at the 2024 Republican National Convention in Milwaukee, Wisconsin on July 15, 2024. (Andrew Caballero Reynolds/AFP via Getty Images)
But his speech also stirred controversy, angering other top Teamsters leaders and some rank-and-file members.
Democrats did not invite O'Brien to speak at their convention in Chicago last month.
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A week before the Democratic National Convention, O'Brien alleged that former President Trump had committed “economic terrorism” after an interview with billionaire businessman Elon Musk in which he praised the tech CEO for firing organizing activists.
“Firing workers for organizing, striking, and exercising their rights as Americans is economic terrorism,” O'Brien said in a statement.
Former President Trump departs from a campaign event at the Central Wisconsin Airport in Mosinee, Wisconsin, on September 7, 2024. Recent polls have Trump trailing Democratic candidate Vice President Kamala Harris in battleground states. (Scott Olson/Getty Images)
Union members were once reliable voters for Democratic candidates.
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But Trump won significant support among working-class voters thanks to the populist, nationalist message he delivered during his three runs for the White House.
Democrats continue to gain support from labor leaders: Most other major labor unions, except for the Teamsters, endorsed Biden early in this election cycle before shifting their support to Harris after the president wrapped up his 2024 campaign.
Get the latest 2024 campaign updates, exclusive interviews and more on Fox News Digital's Election Hub.
