2026 Maine Senate Race

On June 9, 2026 Maine Democrats chose Graham Platner as their nominee to challenge five-term Republican Susan Collins for her Senate seat on November 3. This workspace pairs Kalshi and Polymarket on the question that matters now—does Maine's seat stay Republican or flip to the Democrats—with the just-settled primary kept for context. Both exchanges book the partisan question, so the cross-exchange spread is part of the story: where one book is richer or cheaper than the other is where a new development hasn't fully propagated yet.

Kalshi and Polymarket both book the partisan question: does Maine's seat stay Republican or flip to the Democrats on November 3, 2026? The pies show the full two-way split; the paired market panels below isolate the "Democrats win" price on each exchange so you can read the cross-exchange spread on the single pivotal outcome.

The crowded Democratic field—Governor Janet Mills, Representative Jared Golden, progressive insurgent Graham Platner, Chellie Pingree and several others—settled in the June 9 primary, with Graham Platner taking the nomination. The charts below show how each exchange had the field priced as voting closed; they now carry the resolved result.

• Cross-exchange spread on the partisan market. Kalshi and Polymarket book the same "which party wins" question; sustained divergence on "Democrats win" means one book is slower to price a new development.
• The Platner–Collins matchup. With the nominee set, watch how the general-election price re-rates around the specific Platner-vs-Collins contest and Collins's incumbency.
• News sensitivity. The race has moved sharply on candidate-specific stories; the history panel tracks how the partisan price has drifted toward November 3.