Traders on prediction markets have flipped their bet on which party will control the U.S. Senate after the 2026 midterms, with Democrats now nudging ahead of Republicans for the first time in this market’s history.
As of late Sunday, contracts on platforms tracking the outcome — including Kalshi and Polymarket — put Democrats at about a 51% chance of winning Senate control versus 49% for Republicans. Myriad Markets, owned by Decrypt’s parent company Dastan, pegs the odds of a Democratic sweep of the 2026 midterms at roughly even, about 50-50.
That narrow lead marks a dramatic reversal from a year ago, when markets priced Democrats’ chances at roughly 18%. Kalshi spokesperson Jack Such told Decrypt the race “is now essentially a coin flip, with Democrats having a 51% chance to win.” According to Kalshi data shared with Decrypt, the turnaround has been particularly sharp in the last two weeks: since the start of American military involvement in Iran roughly 16 days ago, the Democrats’ implied probability of controlling the Senate has risen by about 11 percentage points.
The shift underscores how prediction markets quickly incorporate new geopolitical and political signals. Traders have been steadily repricing the Senate race over recent months, and the escalation with Iran appears to have accelerated that movement. The result is surprising to some observers because the Senate map had long been viewed as structurally favorable to President Donald Trump’s party, even as Republicans were expected to face a tougher fight holding the House.
Prediction markets let traders buy and sell contracts tied to real-world outcomes; prices reflect the crowd’s collective expectations and have had notable success forecasting politics in the past, including the 2024 presidential result. Trading volume on the Senate-control contracts remains modest compared with traditional markets but has picked up as the race tightened: Kalshi’s Senate contract has seen over $2.3 million in volume, while Polymarket’s equivalent has traded close to $900,000.
With markets now pricing the chamber as essentially even, traders appear braced for a volatile political cycle in which small moves in polling, policy, or global events could swing the balance of power in the Senate.
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