Incumbent Mike Thompson faces a June 2 top-two primary in California's strongly Democratic 4th District, where his long tenure since 1999 and the district's partisan lean have positioned him as the consensus frontrunner among traders. Self-funded Democratic challenger Eric Jones, who has spent heavily on the race alongside Thompson, has drawn significant attention and fundraising, making both the clear leaders to advance regardless of party. Multiple Republican candidates and one independent filed by the March deadline but trail far behind in resources and visibility. No major developments have shifted the field in the final weeks, leaving the outcome dependent on voter turnout in the solidly blue district.