In California's 4th Congressional District, the June 2026 top-two primary advanced two Democratic candidates—incumbent Mike Thompson and challenger Eric Jones—while all Republican contenders fell short, setting up an all-Democratic general election on November 3. Redistricting under Proposition 50 shifted boundaries to include more Democratic-leaning areas in the Northern California wine country and Sacramento suburbs, producing a district rated Solid or Safe Democratic by major forecasters. This structural outcome, combined with the district's voter registration edge and historical performance, drives trader consensus toward the Democratic Party at 95.9%. A Republican victory would require an unprecedented party switch, disqualification, or write-in surge after certification, scenarios viewed as remote given the confirmed ballot and institutional barriers.