Zach Lahn defeated Rep. Randy Feenstra in the Iowa Republican gubernatorial primary Tuesday, handing President Donald Trump his first major primary loss of the 2026 midterm cycle.
Trump had endorsed Feenstra, the incumbent congressman representing Iowa's 4th Congressional District, in a race widely watched as a test of the president's grip on Republican primaries heading into November.
Lahn, who ran as an outsider challenger, overcame Feenstra's congressional name recognition and the weight of a presidential endorsement to claim the GOP nomination.
The result is a rare setback for an endorsement operation that has posted a strong win record in contested primaries since 2022. It also opens questions about whether Trump's backing can carry candidates in governor's races where voters weigh executive competence alongside loyalty to Washington.
Iowa voted for Trump by double digits in 2024, making the state a near-certain Republican hold in the general election regardless of Tuesday's outcome.
Lahn faces the Democratic nominee in November. No date for that general election contest has been set outside the standard November 3 cycle.