Kalshi and Polymarket Miss South Carolina Senate Election Outcome
United States.- 5 November 2026 | www.zonadeazar.com Prediction market platforms Kalshi and Polymarket recorded one of their first high-profile surprises during the 2026 US midterm elections after Democratic candidate Annie Andrews unexpectedly won a Senate seat in South Carolina.
As late as the afternoon of Tuesday 3 November, both platforms were pricing Republican candidate Darline Graham as having approximately a 70% chance of victory.
However, Andrews prevailed in a traditionally Republican state, prompting renewed discussion about the accuracy of prediction markets as tools for forecasting political outcomes.
An Unexpected Victory in South Carolina
The South Carolina Senate race delivered one of the most surprising results of the US midterm elections.
Annie Andrews, a paediatrician and Democratic candidate, defeated Darline Graham, the sister of the late Republican Senator Lindsey Graham.
The outcome was particularly significant because no Democrat had won a US Senate seat in South Carolina for 28 years.
Furthermore, President Donald Trump had carried the state by approximately 18 percentage points during the 2024 presidential election.
Until the final weeks of the campaign, neither major political party had considered the contest particularly competitive.
Kalshi and Polymarket Favoured Graham
During election day, contracts traded on Kalshi and Polymarket indicated a clear advantage for the Republican candidate.
The implied probabilities were approximately:
- Darline Graham: 70%.
- Annie Andrews: 30%.
These figures reflected market expectations derived from the prices of contracts traded by participants.
Unlike traditional opinion polls, prediction markets allow users to buy and sell contracts whose value depends on the outcome of future events.
The implied probabilities change as trading activity and available information evolve.
More Than $1.48 Billion Traded on US Elections
The 3 November midterm elections represented a significant test for the prediction market industry.
According to reported figures, more than $1.48 billion was traded on contracts linked to the US elections.
The volume demonstrates the growing prominence of platforms such as Kalshi and Polymarket among investors, media organisations and users interested in political events.
This expansion has also increased scrutiny of the reliability of market-implied probabilities.
Other Senate Races Followed Market Expectations
Although South Carolina produced a notable surprise, several other election results developed more closely in line with market expectations.
These included Democratic victories in the Senate contests in Texas and Ohio.
The races had also attracted substantial trading activity.
A comprehensive assessment of prediction market performance will require comparing pre-election probabilities with final results across multiple contests.
Prediction Markets Gained Prominence in 2024
Kalshi and Polymarket attracted significant international attention during the 2024 US presidential election.
Their markets indicated a victory for Donald Trump at a time when some traditional polls suggested a closer contest.
That outcome increased interest in using contract prices as indicators of political expectations.
However, subsequent surprises during US primary elections and Brazil’s presidential election demonstrated that prediction markets can also produce inaccurate forecasts.
Does an Unexpected Result Mean the Market Was Wrong?
Andrews’ victory raises an important question about interpreting probabilities.
A 70% probability does not guarantee that an event will occur. It also implies an approximately 30% chance of the alternative outcome.
Consequently, the victory of a candidate regarded as less likely does not, by itself, establish that a market is statistically inefficient.
Assessing predictive accuracy requires examining numerous forecasts and determining how frequently events occur at different stated probability levels.
South Carolina represents a significant surprise, but a single result cannot establish the overall reliability of prediction markets.
Kalshi and Polymarket Did Not Immediately Comment
Following the result, representatives of Kalshi and Polymarket did not immediately respond to requests for comment.
Both companies have previously emphasised that outcomes assigned relatively low probabilities can still occur.
This distinction is central to understanding the difference between probabilistic forecasting and categorical predictions.
The platforms maintain that their prices reflect participants’ expectations, which can change as new information becomes available.
Industry Impact and Next Steps
The 2026 US midterm elections represent an important opportunity to assess the performance of political prediction markets.
The volume of trading and media attention demonstrates their growing influence on the interpretation of electoral developments.
With more than $1.48 billion traded and an unexpected Democratic victory in South Carolina despite market prices favouring the Republican candidate, Kalshi and Polymarket face renewed questions about the accuracy and limitations of their forecasts.
Further analysis will focus on comparing pre-election expectations with confirmed results across the different states.
Edited by: @fonta
