Incumbent Rep. Mike Thompson (D) faces a competitive primary challenge from well-funded Democrat Eric Jones in California's 4th Congressional District top-two primary on June 2, with a fragmented Republican field of six candidates likely splitting votes and enabling both Democrats to advance to November's general election. Redistricting under Proposition 50, approved in November 2025, redrew boundaries to include conservative Yuba-Sutter counties alongside liberal wine country, narrowing the district's D+17 Cook PVI lean but keeping it rated Solid Democratic. Recent fundraising through March showed Jones edging Thompson in receipts at $3.2 million versus $3 million, fueled by self-funding and progressive donors, while Thompson holds more cash on hand and broad endorsements from Gov. Gavin Newsom and congressional Democrats; a Sacramento Bee voter guide last week highlighted their generational contrast amid absent polls.