A $1,000 Bet Can Shift Election Market Odds on Kalshi and Polymarket, Study Says

A single relatively small bet on Kalshi and Polymarket can significantly change the probability of a given outcome, according to a study by the Anti-Corruption Data Collective (ACDC), which analyzed markets related to US congressional elections.

On these platforms, users trade contracts tied to real-world events — from sports to politics. In election markets, the price of a contract reflects the market’s estimated probability of a candidate winning. When more participants buy contracts on a candidate’s victory, the contract price rises, along with the displayed probability.

The study showed how strongly even a single trade can affect these figures:

• On almost all analyzed markets, a single bet of less than $1,000 was enough to noticeably change a candidate’s displayed odds — for example, from 40% to 50%.
• In most markets, total trading volume was below $1,000, meaning that one individual trade could significantly move the indicator.
• The effect was even stronger for underdog candidates: when a candidate’s odds were 5% or lower, bets of less than $100 were often enough to roughly double the displayed probability.

This is particularly significant because prediction market figures are regularly cited by media outlets and used by campaign teams. As a result, even a temporary price movement could be reported or included in campaign materials as a current measure of a candidate’s chances, creating a risk of manipulation.

At the same time, the researchers do not claim that every sharp change in contract prices is an attempt to influence the market. Users may simply be making risky bets in search of profit.

Kalshi and Polymarket disagreed with ACDC’s conclusions, arguing that markets are capable of quickly correcting such price deviations.