In a crucial meeting with the only major union that hasn't supported her campaign, Harris seeks an endorsement.

One of the country's 10 largest unions, the International Brotherhood of Teamsters boasts over 1.3 million members.

Among the nation's top 10 unions, only the Teamsters have not endorsed Vice President Kamala Harris for the 2024 presidential election.

On Monday, Harris presents her case to the Teamsters, striving to preserve the Democrats' strong backing from labor unions as she confronts Trump.

Earlier this year, the Teamsters met with both Trump and Biden, with the latter being the president who succeeded Harris on the Democrats' national ticket two months ago.

Earlier this month, O'Brien stated that he was eager to discuss the country's direction and the concerns of working people during a meeting with Harris.

In July, O'Brien made history by being the first Teamsters president to speak at a Republican National Convention.

Some top Teamsters leaders and rank-and-file membership were angered by his speech, which led to controversy.

Democrats didn't invite O'Brien to address their convention last month in Chicago.

Before the Democrats' convention, O'Brien accused Trump of "economic terrorism" after Trump praised Musk for firing organizing workers in an interview with Musk.

In a statement, O'Brien emphasized that firing workers for exercising their rights as Americans, organizing, and striking is economic terrorism.

Union workers were once reliable voters for Democratic candidates.

Trump's populist and nationalist messaging has helped him gain support among working-class voters during his three presidential campaigns.

Organized labor leaders continue to endorse Democrats, with most major unions except the Teamsters supporting Biden earlier in the election cycle and later transferring their support to Harris after Biden ended his 2024 campaign.