Senator Roger Marshall recently received an endorsement that would have been unimaginable for a Kansas Republican just ten years ago. The International Brotherhood of Teamsters, including General President Sean O’Brien and the union’s Topeka-based Local 696, backed Marshall’s re-election campaign, citing his support for labor-related legislation including the Railway Safety Act, the Warehouse Worker Protection Act, and the Faster Labor Contracts Act. Although Kansas has not elected a Democratic senator since 1932, limiting the endorsement’s electoral impact, the political signal is notable. A sitting Republican senator winning a national Teamsters endorsement once would have been career-ending for union leadership. Today, it barely provokes a reaction.
This shift traces back to 2024 when the Teamsters polled their 1.3 million members and found no clear majority preference between Kamala Harris and Donald Trump. After Harris secured the Democratic nomination, a majority of responding members actually favored Trump. Consequently, O’Brien’s union chose not to endorse any presidential candidate, marking the first time since 1996 the Teamsters abstained from presidential endorsements, and breaking a streak of endorsing Democrats since 1988. This departure is not a straightforward party switch but rather a refusal to ignore divisions where none can be bridged.
Research from the Center for American Progress Action Fund helps explain this fracturing. Union support for Democrats has grown overall since 2016, but that increase is largely driven by working-class women. Working-class union women favored Harris over Trump by a margin of 14 points in 2024 compared to their nonunion counterparts. For working-class union men, however, the trend ran opposite: they favored Trump by 2 points more than nonunion men, shifting away from the slight Democratic lean seen in 2016 and 2020. Where blue-collar men were once reliably Democratic voters, union membership no longer serves as a strong indicator within this group.
The United Steelworkers (USW) present a useful comparison. While rank-and-file USW members in traditional heavy industry report significant Trump support on the shop floor, the union has not released internal political polling like the Teamsters have. USW leadership has maintained a public and consistent alignment with the Democratic Party. Recently, USW International President Roxanne Brown marked Labor Day alongside Democratic officials including Pete Buttigieg, Summer Lee, Chris Deluzio, and Pennsylvania Governor Josh Shapiro, continuing a long-standing pattern of USW leadership supporting Democrats.
Without member-level polling data publicly available, it is difficult to gauge how closely USW leaders’ politics align with their rank and file. This publication takes no position on the internal political alignment. What is evident is a widening gap between union leadership’s public endorsements and the political sentiments expressed by many rank-and-file members during elections. This has implications beyond the union membership. Companies, and especially their labor relations teams, need to know that their counterparts in contract negotiations speak at the table for their workers. Political disagreements are a surefire route to disunity between international and local, with knock-on effects for employers seeking to wrap up negotiations quickly and get back to business.
The Teamsters have chosen to reveal and confront that gap openly, first by publishing member polling data that showed a fractured base, then by endorsing a Republican senator in a state where the union faces no practical reason to compromise its political stance. Other major unions have not taken similar steps. Whether they can continue to avoid this reckoning indefinitely remains an open question.
