A lot. Polls estimate the percentage of the vote a candidate might win on election day. Players on PredictIt estimate the probability that a candidate will win the election. For example, a candidate in a two-person contest might be leading her opponent 60 percent to 40 percent in the polls. Candidates who lead by a margin this large just before an election almost always go on to win. Consequently, PredictIt may show a probability for the leading candidate of 95 percent or higher.