Incumbent Mike Thompson faces a primary challenge in California's 4th Congressional District from Eric Jones, a Democratic businessman who has drawn endorsements and media attention while leading fundraising among challengers. Multiple Republican candidates, including Sharon Brown and Mandy Ghusar, are also on the June 2 top-two primary ballot, which is expected to split conservative votes in this heavily Democratic-leaning seat. Thompson's long tenure and moderate positioning within the Blue Dog Coalition provide structural advantages, while the recent candidate filing deadline and limited opposition resources among most contenders shape the field. The outcome will determine which candidates advance to the November general election.