James P. Hoffa, the longtime former leader of the International Brotherhood of Teamsters, on Thursday called the union’s decision not to endorse a presidential candidate in the 2024 race a “critical error,” adding that Democratic nominee Kamala Harris was the “correct choice for labor and working families.”

In a statement, Hoffa — who served as the Teamsters’ general president for 23 years before retiring in 2022, and is the son of mid-century labor legend Jimmy Hoffa — said this election was “too important for our union to not do its duty.”

“There is only one candidate in this race that has supported working families and unions throughout their career,” he added, “and that is Vice President Kamala Harris.”

The union announced Wednesday that it would not endorse either presidential candidate. “Unfortunately, neither major candidate was able to make serious commitments to our union to ensure the interests of working people are always put before Big Business,” current Teamsters head Sean O’Brien said in a statement.

Hoffa also characterized the non-endorsement as “a failure of leadership” by O’Brien, his successor. The two have had a fractious relationship since before the 2024 election campaign, The Washington Post has reported.

O’Brien addressed the Republican National Convention in July, a striking departure for the powerful union that has long supported Democrats. He did not publicly endorse Donald Trump, but his presence alone — among GOP lawmakers and a former president who have pushed anti-worker policies — sent shock waves through labor and Democratic circles.

O’Brien had requested to speak at the Democratic convention but did not receive an invitation, according to the union, though several other major labor leaders — and a retired Teamster member who leads a committee that advocated for a 2021 bailout of failing pension plans — did address the convention.

During Hoffa’s tenure, from 1999 to 2022, the union supported the Democratic candidate in every presidential election. In 1996, it did not endorse a candidate, and in decades past has supported Republican candidates including Richard M. Nixon, Ronald Reagan and George H.W. Bush.

The Teamsters have nearly 1.3 million members, according to union numbers. Of its board members, 14 voted to endorse neither candidate this year, while three voted to endorse Harris and none voted for Trump.

“Every major union has endorsed the Harris-Walz ticket,’ Hoffa said in his statement. “But instead of standing in solidarity with all of labor and helping Harris-Walz get over the finish line, the IBT has chosen to take a seat on the sidelines.”