Democratic control of Congress confirms late campaign prediction market tilt

Democrats captured both chambers of Congress after Polymarket and Kalshi had favored that outcome heading into Election Day, according to Seeking Alpha. The result matched a shift in market probabilities that developed through the campaign’s final weeks.

Odds and trading volume aligned around a sweep

Seeking Alpha’s Nov 4, 2026 report, published at 9:00 AM ET, said both platforms had priced the probability of a Democratic sweep above 75 percent before Election Day.

In early Tuesday trading, the sweep probability reached 77 percent on Polymarket and about 75 percent on Kalshi. Those readings made Democratic control of both chambers the favored outcome, but not a certainty.

Trading volume on the sweep exceeded 60 million dollars on Polymarket and 100 million dollars on Kalshi, according to Seeking Alpha. The eventual result supported the markets’ directional assessment in this election.

What it means for prediction markets

• The favored outcome materialized: Democrats’ capture of both chambers aligned with the probabilities on both platforms and the late-campaign movement toward a sweep.
• The platforms showed similar expectations: Polymarket’s 77 percent and Kalshi’s approximately 75 percent readings in early Tuesday trading indicated broadly comparable assessments.
• One result has limits as a performance measure: The outcome confirmed this particular forecast direction; it does not, by itself, establish how well either platform’s probabilities are calibrated across elections.