California's June 2 jungle primary for the 4th Congressional District featured incumbent Democrat Mike Thompson seeking his 15th term after Proposition 50 redistricting added substantial new rural and suburban territory from counties including Placer, Sacramento, and Yuba. Thompson led early returns with roughly 39% of the vote, followed by Republican Ray Riehle at 22% and fellow Democrat Eric Jones at 21%, positioning Thompson and Riehle as the likely top-two advancers to the November general under the state's nonpartisan primary rules. Trader focus centers on Jones's funded challenge and the district's shifted partisan balance, with limited late developments altering the established vote trajectory ahead of final certification.