Redistricting under Proposition 50 placed two Republican incumbents—Ken Calvert, long-serving representative from the former 41st district, and Young Kim, from the prior 40th—into the same newly configured CA-40, which spans eastern Orange and Riverside counties. Both advanced from the June 2026 top-two primary, with Calvert capturing about 35 percent and Kim roughly 21 percent of the vote. The contest has featured heavy negative advertising over Trump alignment, fundraising edges for Kim, and shared emphasis on affordability, though Calvert draws stronger support in Riverside portions of the district. Trader consensus reflects Calvert’s incumbency length and appropriations record keeping him narrowly ahead, while the race remains close due to overlapping voter bases and the absence of a Democratic spoiler in the general election on November 3. Recent internal polls showing a toss-up and continued ad spending could shift margins in either direction before ballots are cast.