The most notable shift in union support for Republicans came last week when the International Brotherhood of Teamsters declined to endorse a candidate in the presidential election, marking the first non-endorsement by the union since 1996. The last time the Teamsters supported a Republican candidate for president was 1988, but like other unions, the Teamsters had widely been seen as a shoo-in endorsement for Democrats in recent decades.

The lack of endorsement angered Democrats and local chapter leaders, but the results of polls conducted by the union of its members showed endorsing Vice President Kamala Harris would have gone against the rank-and-file.

In the electronic member poll released by the Teamsters, 59.6% supported Trump, while only 34% supported Harris.

The support for Trump comes as he has reached out to union members, specifically those in the key rust belt states of Michigan, Wisconsin, and Pennsylvania, and endorsed policies aimed at wooing labor unions. Trump has pushed for increased tariffs on foreign products and protecting domestic energy production, and alongside running mate Sen. J.D. Vance (R-OH), has offered up more pro-union rhetoric. Vance has also styled himself as being friendlier to labor unions than Republicans traditionally.

Harris’s campaign has promised to continue President Joe Biden’s lead as the self-proclaimed “most pro-union president,” pointing to efforts from the administration.

Teamsters General President Sean O’Brien said in a statement announcing “no endorsement” by the union that “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.”

While there has been a shift in union support at the top of the ticket, down-ballot Republican candidates are also seeing unions support them. In New York, a state with several critical House races in November, Reps. Mike Lawler (R-NY) and Marc Molinaro (R-NY) have picked up support from key unions, in a shift from 2022.

Lawler has earned the endorsements of the Rockland County Building & Construction Trades union and other unions that had backed his opponent in 2022, while Molinaro has earned the support of an electrical worker union that previously opposed him, according to the New York Times.

The shift comes as the Republican Party has shifted messaging and some policies among its newer class of politicians toward labor unions, especially as Trump fights to win in the Rust Belt – aiming to replicate higher than usual labor union support compared to other GOP candidates.

In the Teamsters electronic poll, Trump had a 61.7%-35.2% lead over Harris among members in Michigan, a 65.3%-31.4% lead with members in Pennsylvania, and a 57%-40.5% lead with members in Wisconsin. With tight margins in the overall race in those key states, union members could be a key demographic deciding the race.

Despite the strong support, especially in key swing states, a Gallup poll released earlier this month showed 71% of those with a labor union member in their household believe the Democratic Party best serves the interests of labor union members, compared to 17% of those who said the Republican Party best serves the interests of that group.