California’s 4th congressional district holds its top-two primary on June 2, 2026, with longtime Democratic incumbent Mike Thompson seeking reelection in a district that includes Napa, Sutter, and Yuba counties along with portions of Yolo, Lake, Placer, and Sacramento. Thompson faces Democratic challenger Eric Jones and multiple Republican candidates including Ray Riehle, Sharon Brown, and Mandy Ghusar. The district’s strong Democratic lean and Thompson’s nearly three-decade tenure in Congress shape the race, while Jones has invested substantial personal funds in the campaign. Under California’s top-two system, the two highest vote-getters advance to the November general election regardless of party. Recent candidate forums have focused on agriculture, affordability, and tariffs, with no major late developments altering the established dynamics ahead of election day.