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The International Brotherhood of Teamsters (ILT) on Wednesday declined to endorse a presidential candidate after releasing internal polls showing that a majority of its members support 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 has been able to make serious commitments to our union to ensure that the interests of working people always come before the interests of big business,” Teamsters President Sean O’Brien said in a statement. “We have demanded commitments from both Trump and Harris not to interfere in key union campaigns or core Teamsters industries – and to respect our members’ right to strike – but we have been unable to achieve those commitments.”

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

The Trump campaign emphasized the support of “rank-and-file” Teamsters members after the union announced it would not support the union.

“Although the Teamsters Board of Directors does not express formal support, the vast majority of rank-and-file workers in this important organization want to see 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 gave a prime-time speech at this year’s Republican convention but did not appear at the Democratic convention the following month.

The Teamsters, which represents truck drivers, trucking workers and other workers, is the last major union to announce its support for the presidential bid. The country’s other major unions, including the American Federation of Teachers and the United Auto Workers, have endorsed Harris.

The last time the Teamsters sat out a presidential election was in 1996. In the six elections since then, it has supported Democratic candidates, including Trump’s opponent Hillary Clinton in 2016 and Biden in 2020. The union last supported a Republican presidential candidate in 1988, then George HW Bush.

CNN had previously reported that there were strong Trump supporters among union members, although key union leaders supported Harris.

Before Biden dropped out of the race, Teamsters 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, the Teamsters don’t care if you have a ‘D’, ‘R’ or ‘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?”

Endorsement by the Teamsters, which has members from a wide range of industries and a strong presence in key swing states such as Michigan, Wisconsin and Pennsylvania – all of which voted for Trump in 2016 before backing Biden four years later – would have been a critical victory for both candidates.

The Teamsters’ internal data also showed that a poll conducted before Biden dropped out of the race showed Biden had 44% of members supporting him, while Trump had only 36%. Robert F. Kennedy Jr. also participated in that poll, winning about 6% of members. Kennedy has since suspended his campaign and is supporting Trump.

The Teamsters’ support for Clinton and Biden in the last two presidential elections came under previous leadership. While union members are considered a traditionally Democratic voting bloc, Trump has tried to gain a foothold among rank-and-file members.

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

However, Harris does not have as long a tradition of dealing with unions and the working population as the President.

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

This story has been updated with additional information.

CNN’s Kate Sullivan contributed to this report.