Incumbent Mike Thompson seeks his 15th term in California's 4th Congressional District, a solidly Democratic seat redrawn after the 2020 census and further adjusted for 2026, where he faces a primary challenge from Eric Jones, a venture capitalist and nonprofit executive who has raised significant funds and secured endorsements from progressive groups. The June 2 top-two primary features a crowded field that includes multiple Republican candidates such as Sharon Brown and Mandy Ghusar, along with other Democrats and an independent, raising the possibility of vote splitting that could determine which two candidates advance to the general election. Thompson's long tenure, moderate record, and established campaign infrastructure position him as the frontrunner, while Jones's financial edge and mobilization efforts among younger voters create the main point of competition in the coming weeks.