The Forecasting MachineOpen interactive report

Will Ed Markey (D) win the Massachusetts U.S. Senate election on November 3, 2026?

Resolves Yes if Ed Markey (D) is certified as the winner of the Massachusetts U.S. Senate seat contested on November 3, 2026, and No otherwise. If the contest is not decided on election night — because of a runoff, a ranked-choice tabulation, or a recount — it resolves on the final certified result. Declared candidates: Ed Markey (D); John Deaton (R).

Forecasted on

Forecast probabilities

  • Yes: 99.3%
  • No: 0.7%

Reasoning

Markey is overwhelmingly favored to be certified the winner: Yes, 99.3%; No, 0.7%. The race’s strong Democratic baseline is reinforced by large, consistent polling leads and no sign of a late break toward Deaton.

Yes — a wide lead in a reliably Democratic state

The starting point is Massachusetts itself: Republicans have not won a Senate race there since 2010, and forecasters rate this contest Solid or Safe Democratic [a7]. Markey also dispatched Seth Moulton in the primary, leaving the party unified behind him rather than divided after a prolonged nomination fight [e69, e110].

The polling has made the case stronger as Election Day approaches. Markey led Deaton by 19 to 21 points in August; a September UNH poll put him 53–30, and October surveys showed leads of roughly 27 to 28 points, including a Suffolk/Boston Globe result of 60–32 statewide [a9, a10, e16, e71, e91]. These are not merely favorable ratings: they are direct matchups, repeated over time and by different pollsters.

The broader climate does not appear to offer Deaton an opening. Democrats hold a substantial lead in national congressional polling, while a Massachusetts poll found that many voters would be less likely to support candidates associated with Trump [e117, e118, e113]. Markey also has a reported fundraising advantage, and more than 476,000 Massachusetts voters had already cast ballots by October 21 [a7, e78]. Deaton has made a case for independence from both parties and argued in the candidates’ sole debate that he could serve as a swing vote, but there is no evidence that those efforts have narrowed the polling gap [e70, e116].

No — a narrow path through a major surprise

The case against certainty is real but small. Polls can miss, and Deaton has previously attracted a substantial share of the Massachusetts vote; an unexpected event could also disrupt the race. Markey’s age adds a limited personal-health risk, though the available evidence points to no such development. The October lead is so large, and the election so close, that a conventional polling miss is unlikely to be enough.

Why 99.3% Yes

The outside view and the current evidence point in the same direction: Massachusetts is a deeply Democratic state, Markey is an incumbent who cleared his primary decisively, and recent head-to-head polling shows him far ahead. The remaining 0.7% accounts for the possibility of an extraordinary polling error or other disruption—not for evidence of a competitive race.

Update summary

A new Massachusetts poll found that many voters would be less likely to support candidates associated with Trump, offering modest additional context favorable to Markey but no direct evidence of a change in the Senate matchup [e113]. Other newly surfaced polling largely reinforces trends already known, and no major race-specific development has emerged.

Cited evidence