The 40-year-old former state legislator beat a crowded field in Ohio's Ninth District, with state representative Josh Williams second and ex-ICE deputy Madison Sheahan a distant third.
Merrin now faces Democratic Representative Marcy Kaptur, 79, after narrowly losing to her in 2024 in a seat Republicans have since redrawn to be slightly more favourable.
Sheahan had framed her campaign around Trump's immigration crackdown, but Republicans saw her as vulnerable in the general election. Kaptur, in Congress since 1982, remains one of Democrats' most endangered incumbents.
How do cash incentives for immigration arrests affect local policing priorities and community trust?
What paths to justice remain for families when federal prosecutors won't investigate agents involved in civilian deaths?