What Prediction Markets Are Forecasting

Traders on Kalshi are currently giving roughly a 9 in 10 chance that Larry Rhoden wins the 2026 South Dakota Republican gubernatorial runoff by more than 12 percentage points. That's a strong level of confidence, though not a sure thing. To put it another way, if you ran this election 10 times in parallel universes, markets expect Rhoden to clear that double-digit margin in about 9 of them.

The market is structured around a specific question: what will the vote share gap be between the top two finishers in the Republican runoff, scheduled for July 28, 2026. The "above 12%" threshold is the one attracting the most trading activity, and it's currently priced at 90 cents on the dollar.

Why the Market Sees It This Way

A few things are driving that confidence. First, Larry Rhoden isn't a newcomer. He's been South Dakota's governor since January 2025, after Kristi Noem left for the Department of Homeland Security. Incumbents in Republican primaries tend to have structural advantages: name recognition, fundraising networks, and the machinery of the state party behind them. Toby Doeden, the challenger, is a state senator, but he's running against a sitting governor who has already been in the job for over a year.

Second, South Dakota is deeply Republican, and Republican primary voters in the state have historically rewarded the establishment candidate in gubernatorial races. The last several GOP nominees have won their primaries by wide margins. There's also the momentum factor: Rhoden has been making executive decisions, signing bills, and appearing in the news regularly since taking office. Doeden has had to work to get attention.

Third, the runoff structure itself is unusual. South Dakota doesn't normally hold gubernatorial runoffs, but recent changes to election law created this possibility if no candidate clears a threshold in the primary. That adds some uncertainty to the mechanics, but markets appear to be treating Rhoden's incumbency as the dominant factor.

Key Dates and Events to Watch

The primary election comes first, likely in early June 2026. If any candidate wins outright, the runoff never happens and the market resolves accordingly. Watch for polling in the weeks before the primary, particularly whether Doeden can force that runoff at all. If Rhoden's campaign releases internal numbers showing a huge lead, the 90% probability could climb higher. If Doeden starts closing the gap or picks up endorsements from prominent conservative figures, that number could drop.

Also worth watching: any legislative session drama in early 2026. If Rhoden vetoes a popular bill or gets into a public fight with his own party's legislators, it could shift sentiment. Conversely, a strong state-of-the-state address or a budget surplus announcement would likely reinforce his position.

How Reliable Are These Predictions?

Prediction markets have a decent track record on primary elections, especially when incumbents are involved. They're less reliable at extreme probabilities, though. When a market says 90%, it's often closer to reality than a poll, but it's not a guarantee. The margin question adds complexity: even if Rhoden wins comfortably, the exact spread could land below 12% if Doeden runs stronger than expected in rural areas or if turnout patterns favor the challenger.

The bigger limitation is that this market only covers the Republican runoff. The general election in November 2026 is a separate question, and South Dakota's Democratic nominee will almost certainly lose. So while this market tells you about internal GOP dynamics, it doesn't tell you much about who will actually govern the state next year. That's a near-certainty, just not the one this market is measuring.