Betting Markets Favor Trump. But Their Record of Accuracy Is Mixed.

Organizations that track election polls, including The New York Times, currently show Vice President Kamala Harris and former President Donald J. Trump in a dead heat. Election forecasters like FiveThirtyEight, which consider the polls and other data to calculate the candidates’ odds of victory, also see the race as essentially tied.

Another set of websites has a different take. Prediction markets, which allow users to bet real money on election results — more than $100 million on one site alone — are much more bullish on Mr. Trump. These markets are drawing attention, but are they more accurate than the polls, as proponents claim? Do the markets know something that the polls don’t?

Researchers have tried to answer this question over the last few election cycles, though the results have been mixed. Advocates and skeptics agree that there are pros and cons to markets when compared with poll-based forecasts. Markets can sometimes be just as accurate in predicting election outcomes — but there are also good reasons not to take them at face value.

Polls and prediction markets could hardly be more different. Polls attempt to measure what actual voters think by asking a group of them, a sample, how they plan to vote. Polls don’t assign a probability to a candidate’s likelihood of winning — they’re snapshots in time, representing the share of people supporting a candidate at that moment. At their best, polls can be quite accurate, but they are also subject to error and are best understood in aggregate.

Election forecasts — like the ones published by FiveThirtyEight, The Economist, The Hill and election analyst Nate Silver — use the polls and other data such as economic indicators and historical trends to project the likely winner of the election, and the probability that each candidate will win.