Incumbent Mike Thompson holds a 76.5% implied probability in the CA-04 House race due to his primary performance and the district’s strong Democratic lean after 2025 redistricting. Thompson captured 41% in the June 2026 top-two primary, advancing ahead of challenger Eric Jones at 22.2% and Republican Ray Riehle at 20.7%. Forecasters rate the November 3 general election Solid Democratic, reflecting voter registration and historical results in the Napa-Sonoma-Sacramento area. Jones, a former venture capitalist, has self-funded over $10 million and secured some cross-party endorsements, yet no public polls show a shift in the incumbent’s advantage. The market’s pricing aligns with the wisdom of crowds assessing Thompson’s name recognition and institutional support against Jones’s spending in the final weeks.