Short Answer

Ed Markey is likely to win the 2026 Massachusetts Senate race, having secured the Democratic nomination against Republican John Deaton; the market prices this outcome at 96.9%.

1. Market Behavior & Drivers

The market repriced higher following Senator Ed Markey's victory in the September 1 Democratic primary. The probability of a Democratic win in the general election rose from 96.7% before the primary to a peak of 98.1% the day after Markey secured the nomination against challenger Rep. Seth Moulton. This move reflects the resolution of the main source of electoral uncertainty for the incumbent in a heavily Democratic state.
The market has consistently priced a Democratic victory above 96%, treating the outcome of the general election as a near certainty. The brief spike after the primary suggests traders saw the incumbent's nomination as the final hurdle. The price has since settled back to 96.9% on modest volume, indicating the post-primary peak was not sustained and the market has returned to its long-term baseline expectation.
  • Since last update (~28d): The market price for Ed Markey decreased by -2.1pp, widening our edge to +2.1pp.
  • Our confidence score increased significantly by +4.0pp, now reflecting stronger conviction.
  • John Deaton's market probability increased by +0.4pp, while our model remained steady.
  • Incumbent Senator Markey secured the Democratic nomination; forecasters rate the race "Solid D."
  • Massachusetts' strong Democratic history and Markey's polling/fundraising lead persist.

Who Wins and Why

Outcome Market Model Why
Ed Markey 96.9% 99.0% Incumbent Democratic Senator Ed Markey secured his party's nomination for the general election on November 3, 2026.
John Deaton 1.4% 1.0% Republican John Deaton faces a challenging race in historically Democratic-leaning Massachusetts against incumbent Ed Markey.

Current Context

Incumbent Senator Ed Markey won the Democratic primary for the U.S. Senate. Senator Edward J. Markey (D) secured the Democratic nomination for the U.S. Senate on September 1, 2026 [1][2][3][4]. The general election for the Massachusetts U.S. Senate seat is scheduled for November 3, 2026, with early voting taking place from October 17–30, 2026 [2][5][6][7][8][9]. The candidates confirmed for the general election are Democratic nominee Ed Markey, Republican nominee John Deaton, and socialist candidate Joe Tache [2][5][6].
Prediction markets strongly favor Markey to win the November general election. Political forecasters and prediction markets overwhelmingly anticipate Democratic nominee Ed Markey will win the November 2026 general election [10][11][12]. This consensus is attributed to Massachusetts' consistent history of supporting Democratic candidates [10][11][12].
Sources (12)
  1. 1Sen. Ed Markey defeats 47-year-old challenger to win Massachusetts Democratic Senate bidnbcnews.com
  2. 2Ed Markey tops Seth Moulton in US Senate primary, AP projectsbostonglobe.com
  3. 3Markey defeats Moulton in Democratic primary - Boston News, Weather, Sports | WHDH 7Newswhdh.com
  4. 4United States Senate election in Massachusetts, 2026 (September 1...ballotpedia.org
  5. 5Massachusetts elections 2026: Everything you need to know to vote | GBHwgbh.org
  6. 6Massachusetts elections, 2026 - Ballotpediaballotpedia.org
  7. 7Upcoming Electionssec.state.ma.us
  8. 8Session Law - Acts of 2025 Chapter 34malegislature.gov
  9. 9United States Senate election in Massachusetts, 2026 - Ballotpediaballotpedia.org
  10. 10Massachusetts Senate Election Winnerpolymarket.com
  11. 11Will a Democrat Win the Massachusetts Senate Election?lines.com
  12. 12Will the Democrats win the Massachusetts Senat… 95% Yes · Polymarketexplorer.struct.to

2. Price Chart

Historical Price (Probability)

Outcome probability
Date

3. Market Data

Contract Snapshot

A "Yes" resolution for a specific candidate occurs if that candidate's party wins the Massachusetts Senate election; a "No" resolution occurs if they do not win. The market begins on November 3, 8:00 am EST, resolves based on the winning party, and has a maximum payout date of November 3, 2027.

Available Contracts

Market options and current pricing

Outcome bucket Yes (price) No (price) Last trade probability
Ed Markey $0.98 $0.03 97%
John Deaton $0.03 $0.99 1%

Market Discussion

Incumbent U.S. Senator Ed Markey won the Democratic primary on September 1, 2026, defeating challenger U.S. Representative Seth Moulton, and will face Republican nominee John Deaton in the general election scheduled for November 3, 2026 [1][2][3][4][5]. Prediction markets and analytical models consistently indicate a high probability of a Democratic victory, with some forecasts projecting incumbent Markey's win probability to exceed 99% as of September 9, 2026 [6][7][8][9][10][11][12].

Sources (12)
  1. 1Ed Markey tops Seth Moulton in US Senate primary, AP projectsbostonglobe.com
  2. 2Sen. Ed Markey defeats 47-year-old challenger to win Massachusetts Democratic Senate bidnbcnews.com
  3. 3United States Senate election in Massachusetts, 2026 (September 1...ballotpedia.org
  4. 4Sen. Markey defeats Rep. Moulton, will face Deaton in November | Elections | statehousenews.comstatehousenews.com
  5. 5United States Senate election in Massachusetts, 2026 - Ballotpediaballotpedia.org
  6. 6Massachusetts Senate Election Winner Predictions & Odds 2026 | Polymarketpolymarket.com
  7. 7https://polymarket.com/event/massachusetts-senate-election-winnerpolymarket.com
  8. 8Will a Democrat Win the Massachusetts Senate Election?lines.com
  9. 9Massachusetts Senate Election Winner — Compare Odds on 3 Platforms | CoinRithmcoinrithm.com
  10. 102026 Massachusetts US Senate Forecastvotes.decisiondeskhq.com
  11. 112026 Massachusetts US Senate Forecast | DDHQintegration-votes.decisiondeskhq.com
  12. 122026 Massachusetts US Senate Markets | DDHQvotes.decisiondeskhq.com

4. Trust Index

This scorecard was computed Sep 26, 2026 and may not reflect current market conditions.

Octagon Trust Index Kalshi 78 Good
How it adds up
Integrity80% of score82Good
Trade quality20% of score60Caution

Includes the cost to trade: a $1,000 order can't be filled here because the order book is too thin.

Trust score78Good

Weighted blend with hard caps — a critically weak safety pillar, or a severe trading anomaly, caps the total regardless of the rest. Full methodology · About the Trust Index

Trust profile
Integrity4 screens run · 6 don't apply
Market integrity
78Good

Outcome is hard to influence

No suspicious activity on any screen

Screened clean
Large tradesNo single trade dominates the tape. Clear
Thin-volume movesPrice moves carried real volume. Clear
Size patternsTrade sizes look organic. Clear
2 screens not run
Outcome control · doesn't apply to this market type
Thin-leg conviction · doesn't apply to this market type
Info fairness
80Good

Structural prior — no screens apply

No suspicious activity on any screen

Screened clean
Information exposureNo concentrated group can know the outcome materially early. Clear
4 screens not run
Move vs. catalyst · doesn't apply to this market type
Longshot repricing · doesn't apply to this market type
Pre-broadcast certainty · doesn't apply to this market type
Cross-venue timing · doesn't apply to this market type
Resolution quality
92Strong

Resolution mechanism is dependable

No suspicious activity on any screen

Resolution rules read: Clear

Liquidity
76Tradeable

Fills fine at modest size

2 contracts · worst first

John Deaton65
Tradeable · low confidence

Light recent trading — size may not fill near the screen price.

Book spread 25% vs realized 4%
Ed Markey76
Tradeable · low confidence

Light recent trading — size may not fill near the screen price.

Move quality
70Stable

No significant moves

2 contracts · worst first

Ed Markey—
No significant move (6h)

Price was stable over the last 6 hours.

John Deaton—
No significant move (24h)

Price was stable over the last 24 hours.

Rule clarity
100Clear

Counts toward Resolution quality, not here

2 contracts · worst first

Ed Markey100
Clear · high confidence

All checks pass

objective outcome · Clearofficial source · Cleartime boundary · Clear
John Deaton100
Clear · high confidence

All checks pass

objective outcome · Clearofficial source · Cleartime boundary · Clear
Trade quality
60Caution

Order book is thin

Tradable, but expect execution cost beyond small sizes.

Outcome quality 76 (notional-weighted across 2 scored legs)

$100 order: 0.1c slippage (~7% of a 1.4c contract)

$1,000 order: book too thin to fill

$10,000 order: book too thin to fill

Ed Markey76Market scoreLiquidity76Move quality–Rule clarity100
Why 76
Liquidity
76 · Tradeable · low confidence

Light recent trading — size may not fill near the screen price.

Move quality
No significant move (6h)

Price was stable over the last 6 hours.

Rule clarity
100 · Clear · high confidence

All checks pass

objective outcome · Clearofficial source · Cleartime boundary · Clear
John Deaton65Market scoreLiquidity65Move quality–Rule clarity100
Why 65
Liquidity
65 · Tradeable · low confidence

Light recent trading — size may not fill near the screen price.

Book spread 25% vs realized 4%
Move quality
No significant move (24h)

Price was stable over the last 24 hours.

Rule clarity
100 · Clear · high confidence

All checks pass

objective outcome · Clearofficial source · Cleartime boundary · Clear

underwriting_v1.4 · computed Sep 26, 2026

5. What is John Deaton's path to an upset victory against Ed Markey in the 2026 Massachusetts Senate election?

Democratic Party Prediction Market Win Probability97-99% [1][2][3]
Edward Markey Forecasted Win Probability>99% [4][5][6]
Edward Markey Polling Lead (August 2026)19 to 21 percentage points [4][5][7]
John Deaton faces significant challenges in the Massachusetts Senate race. Based on current data, there is no identified viable electoral path to victory for John Deaton in the 2026 Massachusetts Senate election [6][5]. Prediction markets overwhelmingly favor the Democratic party, consistently showing market probabilities for a Democratic victory around 97-99% [1][2][3]. Incumbent Democrat Edward Markey is considered safe to win, with a forecasted win probability exceeding 99% and a projected Democratic margin of 29 percentage points [4][5][6]. Current polling data from August 2026 indicates Edward Markey leading John Deaton by approximately 19 to 21 percentage points, consistently trailing by double digits in head-to-head matchups [4][5][7][8][9]. Furthermore, as of August 12, 2026, Edward Markey's campaign has reported $8,051,970 in total receipts, significantly more than John Deaton's campaign, which reported $1,561,360 [4][5][10].
An upset for Deaton relies on specific external factors and messaging. A theoretical path to victory would require significant challenges to the Democratic nominee, such as deep division following a primary contest, a major scandal, or a highly unfavorable national political environment [9]. This would need to be coupled with the success of specific messaging strategies focusing on Deaton's independent profile and critiques of his opponent's age and tenure, which polling suggests can narrow gaps if voters are exposed to them [9]. John Deaton, a Marine veteran and trial attorney, is running unopposed in the 2026 Republican primary after early state GOP endorsement and has sought to distance himself from Donald Trump to appeal to Massachusetts' moderate, independent-leaning electorate [11].
Sources (11)
  1. 1Massachusetts Senate winner? Odds & Predictions 2026 - Kalshikalshi.com
  2. 2Massachusetts US Senate Winner | Gemini Predictionsgemini.com
  3. 32026 Midterms Prediction Markets — Senate, House & Balance of Powerpredictionmarketspicks.com
  4. 42026 Massachusetts US Senate Forecast | DDHQvotes.decisiondeskhq.com
  5. 52026 Massachusetts US Senate Forecast | DDHQintegration-votes.decisiondeskhq.com
  6. 6United States Senate election in Massachusetts, 2026 - Ballotpediaballotpedia.org
  7. 7Election 2024 Senate Polls - Dave Leip's Atlas of U.S. Presidential Electionsuselectionatlas.org
  8. 82026 Massachusetts Senate - Deaton vs. Markey - RealClearPollingrealclearpolling.com
  9. 9Survey USAsurveyusa.com
  10. 10DEATON, JOHN - Candidate overview | FECfec.gov
  11. 11Trump finishes strong in primaries, looks to close endorsement run with Midas touch in New Hampshire | Just The Newsjustthenews.com

6. How have Republican candidates performed in Massachusetts statewide federal elections since 2000?

Republican success in MA statewide federal elections since 20001 special election (2010 U.S. Senate) [1][2]
Democratic candidate market projection (2026 MA Senate)approximately 98% (prediction markets as of Sep 9, 2026) [3][4]
Incumbent Ed Markey's winning probability (2026 MA Senate)greater than 99% (Decision Desk HQ) [5][6][7][8][9]
Republican candidates have struggled in Massachusetts statewide federal elections since 2000. Since 2000, Republican candidates in Massachusetts have faced significant challenges in statewide federal elections, with their sole notable success being the 2010 special election for U.S. Senate [1][2]. The state has consistently voted Democratic in these contests, and Republican candidates have frequently trailed by large margins in both presidential and senatorial races [10][11][12][13].
Predictions strongly favor a Democratic victory in the 2026 Massachusetts Senate race. Looking ahead to the 2026 Massachusetts Senate race, prediction markets as of September 9, 2026, strongly indicate a Democratic victory [3][4]. Incumbent Ed Markey is projected to hold approximately 98% in market probabilities against Republican challenger John Deaton [3][4]. Furthermore, Decision Desk HQ estimates that incumbent Democrat Edward Markey has a greater than 99% probability of winning against John Deaton [5][6][7][8][9].
Sources (13)
  1. 1List of United States Senators from Massachusetts - Ballotpediaballotpedia.org
  2. 2List of United States senators from Massachusetts - Wikipediaen.wikipedia.org
  3. 32026 Senate Races: All 35 Seats, Market by Marketpredictionmarketspicks.com
  4. 42026 Midterms Prediction Markets — Senate, House & Balance of Powerpredictionmarketspicks.com
  5. 52026 Massachusetts US Senate Forecastvotes.decisiondeskhq.com
  6. 62026 Massachusetts US Senate Forecast | DDHQintegration-votes.decisiondeskhq.com
  7. 72026 Massachusetts US Senate Markets | DDHQvotes.decisiondeskhq.com
  8. 8United States Senate election in Massachusetts, 2026 - Ballotpediaballotpedia.org
  9. 92026 Massachusetts US Senate Markets | DDHQnewsnation-votes.decisiondeskhq.com
  10. 102024 Senatorial General Election Results - Massachusettsuselectionatlas.org
  11. 11Presidential election in Massachusetts, 2024 - Ballotpediaballotpedia.org
  12. 122024 Presidential General Election Results - Massachusettsuselectionatlas.org
  13. 132000 Presidential General Election Results - Massachusettsuselectionatlas.org

7. How do Ed Markey and John Deaton compare on fundraising and campaign spending for the 2026 cycle?

Ed Markey Funds Raised$8,051,970 (as of Aug 12, 2026) [1][2][3][4]
John Deaton Funds Raised$1,561,360 (as of Aug 12, 2026) [1][2][3][4]
Democratic Probability of Victory97-99% (as of Sep 2026) [5][6][7]
Senator Markey significantly outpaces challenger Deaton in campaign finances. As of August 12, 2026, incumbent Democratic Senator Ed Markey reported significantly higher fundraising and expenditures compared to Republican challenger John Deaton in the 2026 election cycle. Markey raised $8,051,970 and spent $8,355,270, while Deaton raised $1,561,360 and spent $848,943 [1][2][3][4]. These figures reflect the pre-primary reporting period and highlight a substantial financial disparity in the race [3][4].
Forecasts overwhelmingly predict a Democratic victory in Massachusetts' 2026 Senate race. As of September 2026, prediction markets and forecast models strongly favor the Democratic candidate for the 2026 Massachusetts Senate seat. Prediction markets consistently place the Democratic party's probability of victory at 97-99% [5][6][7]. Furthermore, Decision Desk HQ forecast models indicate that Edward Markey has a greater than 99% probability of winning the 2026 Massachusetts Senate election [8][3][4][9].
Sources (9)
  1. 1United States Senate election in Massachusetts, 2026 (September 1...ballotpedia.org
  2. 22026 United States Senate election in Massachusetts - Wikipediaen.wikipedia.org
  3. 32026 Massachusetts US Senate Forecast | DDHQvotes.decisiondeskhq.com
  4. 42026 Massachusetts US Senate Forecast | DDHQintegration-votes.decisiondeskhq.com
  5. 5Massachusetts Senate winner? Odds & Predictions 2026 - Kalshikalshi.com
  6. 6Massachusetts US Senate Winner | Gemini Predictionsgemini.com
  7. 72026 Midterms Prediction Markets — Senate, House & Balance of Powerpredictionmarketspicks.com
  8. 82026 Massachusetts US Senate Markets | DDHQvotes.decisiondeskhq.com
  9. 92026 Massachusetts US Senate Markets | DDHQnewsnation-votes.decisiondeskhq.com

8. Which pollsters are actively tracking the 2026 Markey vs. Deaton race, and what are their release schedules?

Key PollstersUniversity of New Hampshire Survey Center, YouGov, University of Massachusetts Department of Political Science, Suffolk University [1][2][3]
General Election DateNovember 3, 2026 [3]
Poll Release ScheduleNo formal or fixed schedule [1][2][3]
Several key pollsters monitor the 2026 Massachusetts U.S. Senate race. Organizations actively tracking the election include the University of New Hampshire Survey Center, YouGov, the University of Massachusetts Department of Political Science, and Suffolk University [1][2][3]. While these groups conduct polling throughout the election cycle, there is no formal or publicly mandated schedule for releasing their results. Instead, polls are issued periodically according to each organization's operational timelines rather than a fixed calendar [1][2][3].
The general election is scheduled for November 3, 2026. This date follows the primary election on September 1, 2026, where incumbent Edward J. Markey (D) defeated Seth Moulton, and Republican John Deaton advanced to the general election [3]. Polling efforts, which previously surveyed hypothetical matchups, are now primarily focused on the upcoming general election phase [3].
Sources (3)
  1. 12026 Massachusetts US Senate Forecast | DDHQvotes.decisiondeskhq.com
  2. 22026 Massachusetts US Senate Forecast | DDHQintegration-votes.decisiondeskhq.com
  3. 3United States Senate election in Massachusetts, 2026 - Ballotpediaballotpedia.org

9. How do major non-partisan political forecasters like the Cook Political Report rate the 2026 Massachusetts Senate race?

Cook Political Report Rating (Sept 9, 2026)Solid D [1][2][3]
Decision Desk HQ Democratic Win Probability99% (Safe Democratic) [4][5]
Prediction Market Incumbent Win Probabilitygreater than 99% [6][7][8][9]
Major forecasters rate the 2026 Massachusetts Senate race as solidly Democratic. The Cook Political Report, a leading non-partisan forecaster, has rated the 2026 Massachusetts U.S. Senate race as "Solid D" as of September 9, 2026 [1]. This classification indicates that the race is not considered competitive. This assessment remained consistent with their rating from September 1, 2026, which also categorized the election as Solid Democratic [1][2][3][6].
Other non-partisan forecasts and prediction markets also confirm a strong Democratic lead. This assessment is further corroborated by other major non-partisan forecasters and prediction markets. Decision Desk HQ's 2026 forecast projects a 99% win probability for the Democratic Party, designating the race as Safe Democratic [4][5]. Data from prediction markets, as monitored by Decision Desk HQ, indicates an over 99% win probability for incumbent Democratic Senator Edward Markey [6][7][8][9]. Across various platforms, prediction markets overwhelmingly suggest a Democratic victory, with some platforms pricing a Democratic win at approximately 98-99% probability [10][11][12]. Senator Markey secured his party's nomination by defeating U.S. Representative Seth Moulton in the primary election on September 1, 2026 [12][13].
Sources (13)
  1. 1MA Senate 2026 | Cook Political Reportcookpolitical.com
  2. 22026 CPR Senate Race ratings - Cook Political Reportcookpolitical.com
  3. 3[PDF] 2026 Senate Race Ratings - The Cook Political Reportcookpolitical.com
  4. 42026 U.S. Senate Forecast | Decision Desk HQvotes.decisiondeskhq.com
  5. 52026 Massachusetts US Senate Forecast | DDHQintegration-votes.decisiondeskhq.com
  6. 6United States Senate election in Massachusetts, 2026 - Ballotpediaballotpedia.org
  7. 72026 Massachusetts US Senate Forecastvotes.decisiondeskhq.com
  8. 82026 Massachusetts US Senate Markets | DDHQvotes.decisiondeskhq.com
  9. 9Massachusetts elections, 2026 - Ballotpediaballotpedia.org
  10. 102026 Senate Races: All 35 Seats, Market by Marketpredictionmarketspicks.com
  11. 11Senate Election Odds | ElectionOddselectionodds.live
  12. 122026 Massachusetts Elections, Odds & Candidates | Prediction Edgepredictionedge.com
  13. 13United States Senate election in Massachusetts, 2026...ballotpedia.org

10. What Could Change the Odds

Key Catalysts

The Massachusetts U.S. Senate general election is scheduled for November 3, 2026 [1][2][3][4][5]. Incumbent Democratic Senator Ed Markey won the Democratic primary on September 1, 2026, against Representative Seth Moulton [3][6]. Republican attorney John Deaton, who ran unopposed in the September 1, 2026, primary, is the Republican nominee for the general election [3][4][7].
Forecasters and prediction markets overwhelmingly favor the Democratic candidate to win the general election, citing Massachusetts' historical Democratic lean and polling margins [1][2][3][4]. Key dates before November 3, 2026, include the voter registration deadline on October 24 and the early voting period from October 17-30 [8][9][10]. The general election ballot also lists Philip Devincentis (American Independent Party), Joseph Tache (Party for Socialism and Liberation), Shiva Ayyadurai (Independent), and Morgan Dawicki (Independent) [5].

Key Dates & Catalysts

  • Expiration: November 03, 2027
  • Closes: November 03, 2027
Sources (10)
  1. 12026 Massachusetts US Senate Forecast | DDHQintegration-votes.decisiondeskhq.com
  2. 2Massachusetts — U.S. Senate — 2026 forecast — Akashicakashic.app
  3. 32026 United States Senate election in Massachusettsen.wikipedia.org
  4. 4Massachusetts Senate Election Winnerpolymarket.com
  5. 5United States Senate election in Massachusetts, 2026 - Ballotpediaballotpedia.org
  6. 6United States Senate election in Massachusetts, 2026 (September 1...ballotpedia.org
  7. 7United States Senate election in Massachusetts, 2026 (September 1...ballotpedia.org
  8. 8Upcoming Electionssec.state.ma.us
  9. 9Massachusetts elections 2026: Everything you need to know to vote | GBHwgbh.org
  10. 10Session Law - Acts of 2025 Chapter 34malegislature.gov