Incumbent Mike Thompson faces a notable Democratic primary challenge from Eric Jones in California's June 2 top-two primary for the 4th Congressional District. Redistricting under Proposition 50 incorporated additional rural and historically conservative counties, though the seat remains solidly Democratic. Both Thompson and Jones have raised and spent millions, with Jones deploying substantial personal funds, while Republican candidates including Sharon Brown and Mandy Ghusar fragment opposition support. Bernie Sanders endorsed Jones. Under the jungle primary rules, the top two vote-getters advance regardless of party, positioning the leading Democrats as the strong consensus advancers with the contest occurring in two days.