Kalshi and Polls Both Called Ohio Midterm Winners
Prediction markets reached high confidence levels weeks before traditional polling did in three competitive races, yet both methods correctly identified the victors.
By Simon Bennett ·
Global trading volume on prediction platforms Kalshi and Polymarket exploded from $26 million in May to $53 billion by July, according to a Pew Research Center analysis. The surge occurred just months before the November midterm election, marking a sharp rise in the use of these financial tools for political forecasting.
The platforms define themselves as marketplaces where participants buy and sell contracts tied to future events. Each contract settles at a stated value, typically one dollar, once the event resolves. This structure allows users to trade based on their expectations of specific outcomes, creating a real-time price for probability.
In Ohio, both traditional polls and prediction markets correctly identified the winners in the U.S. Senate race, the 7th Congressional District, and the gubernatorial contest. However, the two methods diverged on timing. Decision Desk HQ, a forecasting organization, maintained more conservative odds compared to Kalshi throughout the campaigns.
In the Senate race between Sherrod Brown and Jon Husted, Kalshi showed Brown as the favorite as early as September 10. His winning probability climbed steadily to 70.3% by November 1. In contrast, DDHQ never placed Brown above 57% during that same period. RealClearPolling data showed Brown leading in eight of the final ten polls conducted before Election Day.
The 7th District race between incumbent Max Miller and Brian Poindexter highlighted the gap in reaction times. Media coverage of Miller's alleged domestic violence, detailed in a late July report, shifted Kalshi's odds in Poindexter's favor on July 29. Poindexter's winning chance reached 89% by October 23. DDHQ did not declare Poindexter the favorite until October 26, by which time Kalshi already priced his victory at 86.1%.
The gubernatorial race between Amy Acton and Vivek Ramaswamy saw less divergence. Kalshi placed Acton ahead for the first time on August 13. DDHQ followed suit on September 17 after reviewing a batch of polls. Both platforms maintained Acton's lead through Election Day.
Dr. Justin Buchler of Case Western Reserve University noted that predicting Senate seat swings is difficult due to limited data points. Dr. Robert Alexander of Bowling Green State University observed that the prediction markets and polls moved in tandem regarding final outcomes. Alexander stated that the markets likely did not fade from public interest given their alignment with traditional polling.
