Incumbent Democrat Mike Thompson leads the June 2, 2026, top-two primary for California's 4th Congressional District following redistricting that added significant new territory to the seat. Early vote tallies show Thompson ahead of Republican Raymond Riehle and fellow Democrat Eric Jones, with the top two finishers advancing to the November general election under California's nonpartisan primary system. Thompson, seeking his 15th term, secured party endorsement and maintains strong name recognition in the altered district. The outcome hinges on final vote consolidation across counties, as the race features multiple Republican and Democratic challengers splitting the field. No major last-minute developments have altered the early positioning ahead of full certification.