The United States legislative elections take place at a time of expansion of so-called prediction markets, platforms on which users can bet money on possible outcomes of events, including electoral disputes.
The use of these platforms in elections, however, worries experts due to the risk of spreading false information and misinterpretations about the results of the polls.
Experts warn that the percentages displayed on these platforms can be interpreted as practically guaranteed results, although they only represent estimates. There are also situations where political groups try to influence these probabilities.
If the result of the polls is different from that indicated by the prediction markets, some voters may interpret this divergence as an indication of fraud, even if it does not represent an irregularity.
Platforms like Polymarket and Kalshi allow users to negotiate contracts whose value depends on election results. Despite the growth of this market, surveys indicate that the majority of Americans are against placing bets on elections.
In Brazil, the offering of contracts linked to electoral results has been prohibited since May 2026. A resolution by the National Monetary Council (CMN) began to prevent financial operations related to political and electoral events, as well as other events not linked to economic and financial indicators. The measure also led to the blocking of platforms such as Polymarket and Kalshi in the country.
The probabilities published by the two platforms also began to appear in the coverage of major media outlets, expanding the presence of prediction markets in electoral news.
"They have increasingly become part of how Americans understand elections," says Davina Hurt, director of government ethics at Santa Clara University's Markkula Center for Applied Ethics.
"We are reaching a point where the expectations of financial markets have more weight in the public's mind than votes," he adds.
Prediction markets are becoming popular in the US, but they still face legal disputes over which rules they must follow. The debate is whether these platforms should be regulated like commodity markets, which trade certain assets and contracts, or whether they should be subject to betting laws.
Kalshi claims that the information offered by its platform is different from that presented by traditional electoral surveys. The company recognizes, however, that the published probabilities do not guarantee that a given result will materialize.
According to the company, any attempts to manipulate the probabilities tend to be offset by negotiations carried out by other users of the platform.
"Kalshi should be seen as a complement to traditional searches," Elisabeth Diana, the platform's communications director, told AFP.
Despite these explanations, experts warn that percentages can be confused with already defined results. The risk increases because Polymarket and Kalshi also publish their estimates on social media, expanding the reach of this information.
Hurt points out that, even when a platform indicates a high probability, this does not mean that the result is guaranteed.
"A high probability is not a promise (...) When a prediction turns out to be wrong, it doesn't mean the choice was wrong. However, people will interpret it that way," says Hurt.
An episode that occurred in June, in the primary elections for Los Angeles Mayor, showed how market probabilities can be confused with the results of the polls.
After the defeat of Republican Spencer Pratt, right-wing influencers made accusations of fraud, citing platform estimates that indicated the candidate's chances of advancing to the general election.
Some of the publications with false information on social network X appeared identified as "paid partnership". The episode provoked criticism and led Polymarket and Kalshi to adopt measures in relation to the dissemination of this type of content.
"The June primary showed how expectations about an election can be confused with the results," said Michael Sánchez, spokesman for the Los Angeles County Voter Registration Office.
In a document obtained exclusively by the AFP agency, Kalshi instructed its partners not to question official election results without providing reasons for doing so.
According to the document, partners "should not question the integrity or accuracy of any official vote count result, court decision or other official or formal determination linked to the electoral process."
The company also stated that it will break contracts with partners who make accusations without proof that "an election result was manipulated, rigged or compromised."
Polymarket did not respond to requests for comment.
The advance of prediction markets also worries election authorities. Jared DeMarinis, responsible for administering elections in the state of Maryland, called for an assessment of the legality of betting related to electoral disputes in the state.
In an interview with AFP, DeMarinis stated that he prohibited poll workers from betting on election results.
"Now more gasoline has simply been added by involving money in this. What we least want is for the legitimacy of the result to be questioned," he stated.
