The Teamsters withholding an endorsement from Harris this week — after internal polling showed most respondents backing Trump — is sparking fresh concerns that the GOP nominee could have higher-than-expected support among union members, especially men. Labor leaders in other sectors attest that, like in 2016 and 2020, the former president has maintained a grip on key parts of their rank-and-file despite his anti-union record. Privately, Democrats say Harris still has work to do to win over older, white, working-class voters who make up a large portion of the electorate in the Rust Belt and have been hit by high prices.

“Candidly, Trump has a solid, solid base of working-class people that have bought into his message,” said Jimmy Williams, president of the International Union of Painters and Allied Trades, which has endorsed Harris. “It’s movable and it's been moving. But it's not like some tide that's turned.”

Some Teamsters leaders have questioned the methodology of the polling showing Trump winning majority support among the union’s members. But one pro-Harris union official, who was granted anonymity to speak freely, spoke in dire terms about it. The person said it is a “red flag” that is reminiscent of the 2016 election, when Hillary Clinton underperformed among union households despite winning the majority of top labor endorsements.