In California's 4th Congressional District, the June 2, 2026, top-two primary features incumbent Democrat Mike Thompson facing a notable intra-party challenge from Eric Jones, a former venture capitalist who has out-raised the longtime representative and secured an endorsement from Sen. Bernie Sanders. Six Republican candidates and one independent are also on the ballot, with vote splitting among them likely to shape which two contenders advance under the state's nonpartisan primary rules. Thompson's 28-year tenure and moderate positioning provide structural advantages in this safely Democratic district, while Jones's financial momentum and outsider appeal represent the main recent catalyst shifting trader attention toward a potential upset in the primary outcome. The race remains fluid with under three weeks until voters decide the general election matchup.