The Forecasting MachineOpen interactive report

Which party will win the 2026 US Senate election in Maine?

The election will be held on November 3, 2026. The Republican incumbent is Susan Collins, and the Democratic challenger is Troy Jackson.

Forecasted on

Forecast probabilities

  • Democratic Party: 66.8%
  • Republican Party: 32.9%
  • Other / Independent: 0.4%

Reasoning

Troy Jackson is favored, but not by enough to make this a safe call: the final polling points toward him, while Susan Collins’s history of winning voters who usually lean Democratic keeps the race genuinely competitive. The forecast is Democratic Party: 66.8%; Republican Party: 32.9%; Other / Independent: 0.4%.

Democratic Party — 66.8%: A late polling edge in a Democratic-leaning year

The strongest case for Jackson is that his lead appears in several late polls, not just one: the final New York Times/Siena survey put him ahead 51–45, Echelon showed him up 51–44, and Marist had him ahead 49–47. Fox News and Trafalgar, by contrast, found a tie, and the polling average showed only a narrow Jackson lead. Taken together, the evidence suggests an advantage rather than a commanding one. [e1554, e1381] [e1552, e1561]

The broader climate points the same way. Democrats led the generic ballot, and a late national survey found voters preferred a Democratic-controlled Congress; Siena also found Democrats leading among independents across the battleground states it surveyed. That matters in Maine, where Collins’s strength has long depended on winning beyond the Republican base. [e1575, e1576] [e1569]

Republican Party — 32.9%: Collins has beaten the usual rules before

Collins is not an ordinary incumbent facing ordinary headwinds. She won in 2020 by 8.6 points even as Maine backed Joe Biden, and she has repeatedly shown an ability to win crossover voters when polls and partisan lean suggest otherwise. Her seniority and record of securing federal funding for Maine give her a concrete argument for another term; Republican-aligned groups have also spent heavily on her behalf. [a1, a7] [e1557, e1345]

But the conditions are unusually difficult for that playbook. Collins is running in a midterm under unified Republican control, amid a Democratic-leaning national mood, and late polling generally shows Jackson ahead. Her campaign’s closing ad attacking Jackson’s background as a logger drew criticism as tone-deaf—an effort that could reinforce, rather than counter, the challenger’s working-class appeal. Collins’s history makes an upset plausible, not the likeliest outcome. [a1, e1576] [e1564]

Other / Independent — 0.4%: A procedural possibility, not a plausible winner

Six write-in candidates have qualified, so if neither major-party candidate wins a majority of first-choice votes, Maine could use ranked-choice tabulation. That creates a route for additional counting, not a credible path for an independent candidate to finish first. [e1563, e1570]

Why the probabilities remain close

The evidence favors Jackson, but the evidence does not erase Collins’s unusual record. Recent polls, the national environment, and the late movement of the campaign all lean Democratic; tied surveys, Collins’s financial and institutional advantages, and her past polling overperformance argue against treating that lead as secure. The resulting forecast gives Jackson the edge at 66.8%, leaves Collins a substantial 32.9% chance, and assigns only 0.4% to an Other / Independent winner.

Update summary

A final New York Times/Siena poll released November 1 showed Troy Jackson ahead of Susan Collins by six points, strengthening the case for Jackson beyond the earlier narrow polling leads [e1554]. Newly released national polling also showed a Democratic preference for congressional control and Democratic strength among independents, though this largely reinforces the political climate already reflected in the forecast [e1576, e1569].

Cited evidence