Incumbent Mike Thompson and Democratic challenger Eric Jones lead trader expectations to advance from California's 4th Congressional District top-two primary on June 2. Thompson's long tenure and moderate profile have sustained broad support in the D+8 district, while Jones has drawn attention through strong fundraising, progressive endorsements, and focus on housing affordability. A crowded Republican field risks vote fragmentation that favors both Democrats clearing the primary. Recent campaign activity, including mutual attacks between the top Democratic contenders and limited opposition spending, has reinforced this positioning without shifting the underlying partisan math. The June 2 results will determine the general-election matchup in November.