California’s 4th Congressional District held its top-two primary on June 2, 2026, with longtime Democratic incumbent Mike Thompson seeking a 15th term against Democratic challenger Eric Jones and multiple Republican candidates. Thompson, who serves on the House Ways and Means Committee, led the field while Republican Ray Riehle placed second, allowing both to advance to the November general under the state’s nonpartisan primary rules. Jones finished third despite endorsements from progressive groups and personal spending. The district’s partisan lean and Thompson’s established fundraising and name recognition shaped candidate positioning ahead of the vote, with no major late developments reported in the final weeks.