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Polymarket, election betting sites favor Trump over Harris

Topline

With polls ending in just a few hours, betting markets are firmly in favor of former President Donald Trump securing a second term as president, even as poll-based prediction models suggest the candidates are in a dead heat.

Important facts

Polymarket: Perhaps the most famous election betting provider, the blockchain-based site is most heavily tilted toward Trump, giving him an implied 61% chance of victory, compared to 39% for Harris (as of approximately 4:00 p.m. EST).

Kalshi: The New York-based prediction platform favors Trump by a margin of 58% to 42%, a significant change from Saturday, when Harris was briefly ahead on the site; Unlike Polymarket, Kalshi operates legally in the US, as does competitor PredictIt and brokerage firms Robinhood and Interactive Brokers.

PredictIt: The site leans most heavily toward Harris. PredictIt calculates a rate of around 49% for Harris compared to 51% for Trump.

Robinhood: The retail giant is the latest big entrant into election betting, giving Trump a win probability of about 60% compared to 42% for his Democratic opponent.

Interactive Brokers: Billionaire Thomas Peterffy's digital broker offers election bets through its subsidiary ForecastEx, pricing in odds of about 57% for Trump and 41% for Harris.

Betfair and Smarkets: The London-based sites are not open to Americans, but both peg similar odds of a Trump victory, with Betfair pegging the Republican by a 61% to 39% margin and Smarkets by a 61% margin 41% favored.

Big number

58%. These are the betting market's aggregate odds for a Trump win, according to the Election Betting Odds Tool, which tracks odds from Betfair, Kalshi, PredictIt, Polymarket and Smarkets.

Cons

Polling data suggests Harris and Trump are nearly evenly matched on Election Day. FiveThirtyEight's forecasts favor Harris by a margin of 50% to 49%, while Silver Bulletin, the model from statistician and Polymarket consultant Nate Silver, leans toward Harris by a tiny margin of 50.02% to 49.99%. The difference between betting market odds and survey-based prediction models has been a major topic of discussion in recent weeks. Some argue that betting markets are a better predictive factor because bettors have a financial incentive to bet on the candidate who is more likely to win, and skeptics point to the potentially pro-Trump demographic among bettors as an explanation for the bias.

How does election betting work?

Websites offer users contracts with prices tied to the real-time market-driven odds of a particular candidate. Each contract pays $1 if the bettor chose the winning candidate and $0 if his bet was wrong. So at current odds, a contract for Trump would cost about $0.57 and one for Harris would cost about $0.44 on Robinhood, with each contract having the same binary return of $0 or $1 would be offered. Election betting sites operating legally in the US have comparable limits: Robinhood allows 5,000 contracts per user and PredictIt allows $850 per user on each election market.

When are election bets settled?

It varies depending on the platform. Polymarket's main market will pay off when the Associated Press, Fox News and NBC News newsrooms call the election in favor of a candidate (so possibly as early as this week). Robinhood will pay winners on January 7, a day after Congress certifies the results, Kalshi will pay on Inauguration Day on January 20, and PredictIt says it will pay out when “any ambiguity or uncertainty is cleared up before the market “.

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