California’s new congressional map, enacted through Proposition 50 in November 2025, serves as the central driver of trader expectations. The legislature-drawn boundaries, adopted after Texas redistricting and approved by voters, shifted several Republican-leaning districts toward Democrats, reducing competitive seats to roughly four while creating an expected net gain of three to five Democratic seats. Current forecasts project Democrats holding 48 of California’s 52 districts, consistent with the market’s heavy weighting on that outcome. The top-two primary system and limited remaining battlegrounds in areas such as the Central Valley and San Diego further consolidate Democratic advantages. National midterm dynamics and recent primary results have reinforced this positioning without introducing major late shifts.