Andrews victory in South Carolina defies prediction markets’ Republican lean

Democrat Annie Andrews defeated Republican Darline Graham for a United States Senate seat in South Carolina, according to Reuters. The outcome ran against the favorite on both Kalshi and Polymarket.

A historic result against market expectations

As of late afternoon Tuesday, Kalshi and Polymarket had implied a 70 percent probability that Graham would win, according to Reuters. Andrews’ victory therefore delivered a loss for the outcome both platforms had favored at that point.

Andrews is the first Democrat to win a Senate seat in South Carolina in 28 years. That milestone makes the result significant beyond the gap between market expectations and the eventual winner.

A prominent test for election markets

The upset marked prediction markets’ first high-profile miss of the midterm elections, according to Reuters. The cycle attracted more than 1.48 billion dollars in wagers.

The reported probability is a snapshot from late afternoon Tuesday, rather than a closing forecast. It establishes that Graham was favored then, but the supplied reporting does not show how either platform’s prices changed afterward.

What it means for prediction markets

• A favorite is not a certainty: A 70 percent implied chance leaves room for defeat. This result alone does not establish whether those probabilities were well calibrated.
• Timing matters: Comparisons with the outcome should identify the late-afternoon Tuesday snapshot rather than treat it as the markets’ final assessment.
• Wagering scale does not guarantee accuracy: The cycle’s more than 1.48 billion dollars in wagers provides context for the attention on this miss, not proof of forecasting reliability.