Kalshi hit $53 billion in July as Ohio voters split from polls

Global trading volume for prediction market platforms Kalshi and Polymarket reached $53 billion in July 2026, according to a Pew Research Center analysis. This figure was more than double the $26 million recorded in May 2026. The surge was driven largely by sports trading, but the platforms also provided early signals in the November midterm elections. In Ohio, both Kalshi and traditional polling organizations correctly identified the winners of the state's major races, though they arrived at those conclusions through different timelines.

In the U.S. Senate race, Democrat Sherrod Brown defeated Republican Sen. Jon Husted. Kalshi odds for Brown began rising on Sept. 10, when his probability of victory hit 51.1%. By Nov. 1, that figure climbed to 70.3%. During that same period, the forecasting service DDHQ never placed Brown above a 57% chance of winning. RealClearPolling data showed Brown leading in eight of the final ten polls conducted before Election Day.

The 7th Congressional District race saw a similar divergence in timing. Democrat Brian Poindexter defeated incumbent Republican Rep. Max Miller. Kalshi first listed Poindexter as the favorite on July 29, following widespread media coverage of domestic violence allegations against Miller. His odds peaked at 89% on Oct. 23. DDHQ maintained Miller as the favorite until Oct. 21, when the odds reached a 50-50 split. The service did not declare Poindexter the favorite until Oct. 26, at which point Kalshi already gave Poindexter an 86.1% chance of winning by a margin of eight points.

The gubernatorial race between Democrat Dr. Amy Acton and Republican Vivek Ramaswamy showed closer alignment between the two data sources. Kalshi first projected Acton ahead of Ramaswamy on Aug. 13. DDHQ reached the same conclusion on Sept. 17, following a series of September polls. Both platforms maintained Acton as the favorite through Election Day.

Dr. Justin Buchler, an associate professor of political science at Case Western Reserve University, noted that predicting seat swings in Senate elections is difficult because only a third of the Senate is up for election in any given year. He cited the death of Sen. Lindsey Graham and the underperformance of his sister, Darline Graham, as idiosyncratic factors that complicate forecasting. Dr. Robert Alexander, a political science professor at Bowling Green State University, observed that the prediction markets and polls generally moved in tandem. He said the platforms did not appear to be a temporary trend, noting that they aligned with traditional forecasting methods without major misses.

Fidelity defines prediction markets as marketplaces where participants buy and sell contracts tied to the outcome of future events. Contracts settle at their stated value, typically $1, once the event resolves. The platforms allow users to trade based on their expectations of specific, clearly defined outcomes.