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The International Brotherhood of Teamsters on Wednesday withdrew its endorsement of a presidential candidate after internal polls were released showing a majority of members backing former President Donald Trump over Vice President Kamala Harris.

It is the first time in nearly three decades that the union has not endorsed a presidential candidate.

“Unfortunately, neither major candidate was able to make any meaningful commitments to our union to ensure that the interests of working people are always put before big business,” Teamsters President Sean O’Brien said in a statement. “We asked both Trump and Harris for commitments not to interfere with critical union campaigns or core Teamsters industries — and to respect our members’ right to strike — but we were unable to secure those commitments.”

Before the decision, the Teamsters shared internal data showing a majority of members backed Trump over Harris. According to an electronic membership poll that was initiated after President Joe Biden withdrew from the race, about 60% of members believed the union should support Trump, while 34% backed Harris. About 6% said they supported another candidate.

Trump’s campaign emphasized the support of “rank and file” Teamster members after the union announced it would not endorse the union.

“While the Teamsters Board of Directors does not formally endorse the White House, the overwhelming majority of the ordinary working men and women of this important organization want President Donald Trump back in the White House,” the Trump campaign said in a press release, citing internal polling data.

Harris met with Teamsters leaders on Monday. O’Brien had a prime-time speaking slot at the Republican National Convention this summer but did not appear at the Democratic convention the following month.

The Teamsters, which represents truck drivers, freight workers and other employees, is the latest major union to announce a presidential endorsement. The nation’s other major unions, including the American Federation of Teachers and the United Auto Workers, have backed Harris.

The last time the Teamsters withdrew from a presidential election was in 1996. The union has supported Democratic nominees in the next six elections, including Trump’s opponents Hillary Clinton in 2016 and Biden in 2020. The union last supported a Republican presidential candidate in 1988, with an endorsement of George H.W. Bush.

CNN previously reported that many union members supported Trump, even as key labor leaders backed Harris.

Before Biden withdrew from the race, Teamster officials had suggested to various stakeholders that the union could remain politically neutral this cycle for the first time in decades.

“At the end of the day, Teamsters don’t care if you have a ‘D’ or an ‘R’ or an ‘I’ next to your name. We want to know one thing,” O’Brien said at the RNC. “What are you doing to help American workers?”

An endorsement from the Teamsters, which draws from across sectors and has a strong presence in key swing states like Michigan, Wisconsin and Pennsylvania — all of which voted for Trump in 2016 before backing Biden four years later — would have been a crucial victory for either candidate.

The Teamsters’ internal data also revealed that a town hall poll conducted before Biden dropped out of the race showed him with 44% of members supporting him, compared to 36% for Trump. That poll included Robert F. Kennedy Jr., who had about 6% of members supporting him. Kennedy has since suspended his campaign and endorsed Trump.

The Teamsters’ endorsements of Clinton and Biden in the past two presidential cycles came under previous leadership. While union members are seen as a traditional Democratic voting bloc, Trump has worked to make inroads among rank-and-file members.

Biden has long enjoyed strong union support. He became the first sitting president to visit a picket line last September and frequently used a version of the phrase “The middle class built America, and unions built the middle class” in many of his campaign speeches during his time as a candidate. Harris has also begun using the phrase.

But Harris doesn’t have as long a history with unions and working people as the president does.

Her running mate, Minnesota Governor Tim Walz, is himself a former union member and public school teacher.

This story has been updated with additional information.

CNN’s Kate Sullivan contributed to this report.