Incumbent Democrat Mike Thompson and challenger Eric Jones advanced from the June 2026 top-two primary in California's 4th Congressional District, eliminating all Republican candidates and setting up a same-party general election on November 3. Multiple forecasters rate the seat Solid or Safe Democratic following Prop. 50 redistricting, which preserved a partisan lean favoring Democrats in this Northern California district covering Napa, Sonoma, and surrounding counties. With no opposing-party nominee on the ballot, trader consensus reflects the structural certainty of a Democratic winner, consistent with the district's voter registration and historical results. Late developments such as candidate-specific scandals or unusually low turnout could theoretically alter the specific nominee but are unlikely to shift the party outcome absent unforeseen events before Election Day.