The June 2026 top-two primary in California's 4th congressional district advanced two Democratic candidates—incumbent Mike Thompson and challenger Eric Jones—while the leading Republican finished third and failed to reach the general election ballot. Multiple nonpartisan forecasters rate the seat Solid or Safe Democratic based on voter registration, recent redistricting that preserved the district's overall lean, and Thompson's long incumbency. These structural factors explain the overwhelming market pricing for a Democratic winner. A Republican victory would require an unprecedented reversal, such as both Democratic nominees withdrawing before November 3, an event with no precedent in comparable districts.