Brennan Center study finds prediction markets sway voters

A study by the Brennan Center for Justice found that prediction market data shapes voters' views in a way comparable to traditional polling. The study also found that more than 80% of respondents favour tighter regulation of political event contracts or support banning them outright.

According to the Brennan Center, a common problem is that lots of voters conflate how a conventional survey is conducted with how a live prediction market operates. A survey result is derived from questioning a representative sample of American voters about their voting intentions, whereas market odds reflect the prices at which participants trade contracts tied to a given outcome, the centre explained.

Only 20% of those surveyed consider political prediction markets accurate, and just one-third think election-based event contracts mirror wider public sentiment, the report found. Even so, the trading data clearly influences expectations: when markets favoured a candidate, respondents were 10 to 20 percentage points more inclined to expect that candidate to prevail, no matter what polling showed.

The reverse can happen too, per the Brennan Center: respondents were 11 percentage points less inclined to expect victory for a candidate sitting at 33% odds on a leading prediction market, and 19 percentage points less inclined for one at 16% odds. Market odds influenced perceived electability about as much as conventional polls did, and more than any background characteristic of the candidates, such as demographics, occupation or prior experience.

When asked about regulation, 23% of those surveyed wanted regulators to stop particular political market contracts, and 16% backed outlawing the industry entirely, the study found.

It was reported that the concerns arise as exchanges form partnerships with media organisations across digital, print and television formats. It also reported that major all-or-nothing exchanges showed Assemblyman Zohran Mamdani ahead before Election Day in the 2025 New York City mayoral election, and that predictions were correct in the 2024 presidential election.