Polymarket, Election Betting Watch Trump Pass Harris

Topline

Former President Donald Trump has surged on betting sites as more states close their polls, reversing a shrinking lead over Vice President Kamala Harris in the betting odds after the first major polls closed, while poll-based prediction models suggested the Candidates who did so were locked in a dead heat before election day.

At Northwest Activities, people cast their in-person early voting for the 2024 general election … (+) Center on October 29, 2024 in Detroit, Michigan.

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Important facts

Polymarket: The blockchain-based site, perhaps the most famous election betting provider, was still leaning toward Trump after the initial closures, giving him an implied chance of victory of 92.7%, compared to 7.5% for Harris (as of about March 22: 45 p.m. EST).

Kalshi: The New York-based prediction platform favors Trump by a margin of 89% to 11%, 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 most Harris-leaning site still favored Trump as of 10:45 p.m., with PredictIt rating Trump 89% to 14%.

Robinhood/Interactive Brokers: The retail giant is the latest big entrant into election betting — and like Interactive Brokers, offers election betting through ForecastEx — giving Trump a win probability of about 90% compared to 12% for his Democratic opponent.

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 93% to 8% margin and Smarkets by a 94% margin 5% favored.

By the time the first major polls closed at 6 p.m. EST, odds on high-profile betting platforms were around 60% for Trump and 40% for Harris.

Big number

90.3%. These are the betting market's aggregated odds for a Trump win as of 10:45 p.m. EST, according to the Election Betting Odds Tool, which tracks odds from Betfair, Kalshi, PredictIt, Polymarket and Smarkets.

What do other indicators say?

According to the Associated Press, as of 10:45 p.m. EST, Trump had received 210 votes in the Electoral College, while Harris had 112 votes. The New York Times' live presidential forecast said just before 10:45 p.m. that Trump was “likely” to win the election with an 85% chance of victory. Forbes provides live updates on the election results here.

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.

What do the betting odds show for Senate and House control?

Currently, Democrats have control of the Senate with 51 seats, compared to Republicans' 49 seats, and Republicans have control of the House of Representatives. The Election Betting Odds Tool, which compiles odds from multiple sites, is heavily leaning toward Republicans taking control of the Senate from Democrats by a margin of 97% to 3% as of 10:45 p.m. EST ). The same website favors Republicans taking control of the House by a margin of 79% to 21%.

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 “.

CORRECTION (11/5): This story has been updated to clarify that Interactive Brokers and Robinhood move to the same exchange and cannot have different odds.