Redistricting under Proposition 50 has shifted California’s 1st Congressional District westward to incorporate Democratic-leaning areas of Sonoma County, including Santa Rosa, transforming a seat that favored Republicans by roughly 25 points in 2024 into one projected to lean Democratic by about 12 points. This structural change underpins trader consensus favoring state Sen. Mike McGuire (D) at 94.7% to incumbent Rep. James Gallagher (R) at 4.5% for the November 3 general election. Gallagher secured the special election for the short term ending in January and advanced narrowly from the June primary under the new lines, yet forecasts from multiple outlets assign McGuire a commanding edge consistent with the altered voter composition. Potential shifts could arise from unusually high Republican turnout, late developments, or campaign events in the final weeks before mail ballots begin arriving.