Massachusetts's strong Democratic lean and consistent polling keep the 2026 Senate race heavily tilted toward incumbent Ed Markey over Republican John Deaton, with recent surveys showing leads of roughly 20 points. Markey's decisive primary victory over Seth Moulton on September 1 reinforced party unity, while Deaton's nomination has produced limited momentum in a state where Democrats have won recent Senate contests by wide margins. Trader consensus on Polymarket centers the most probable victory margins in the 25-35 point range, reflecting stable fundamentals, low Republican crossover potential, and the absence of major late-cycle shifts. A narrower outcome would require unusually high Republican turnout or unexpected national headwinds, while wider results remain possible if Democratic participation exceeds expectations in the final weeks before November 3.