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BetOnline made Ken Paxton's margin of victory 20 points or more against John Cornyn in the Texas GOP primary runoff as the 2-1 favorite
Paxton would go on to beat Cornyn by 27 percentage points when all was said and done
Paxton is now a very slight favorite to beat Democratic candidate James Talarico in the general election
All above odds as of May 15, 2026
Most news outlets had already written off long time incumbent Texas Republican Senator John Cornyn heading into Tuesday's GOP runoff primary.
Nearly all, however, were stunned by the margin of victory Attorney General Ken Paxton registered when all was said and done.
The gambling world should not have been.
Gambling911.com had published the margin of victory odds for Paxton days in advance at greater than 20 point or greater as the 2/1 favorite, courtesy of BetOnline.
Paxton ended up beating Cornyn by 27 percentage points once all votes at come in.
This ended up being the largest primary loss for a sitting U.S. senator in nearly five decades.
New York Magazine / Intelligencer characterized it as a “stunning upset,” noting that Cornyn had massive financial advantages and statewide name recognition yet was still “crushed." while the Washington Post deemed the victory as “historic,” emphasizing that Cornyn had been viewed for years as one of the safest Republican incumbents in the country.
Polling just days before showed a tight race.
The statewide survey, conducted by the University of Houston’s Hobby School of Public Affairs, found Paxton garnering 48% of the vote to Cornyn’s 45% among likely GOP runoff voters. Fielded from April 28 to Friday, the poll surveyed 1,200 voters and yielded a margin of error of +/-2.83 percentage points.
In the end, the gambling sites had it right. BetOnline's odds are based on action from recreational and sharp gamblers alike. It operates as a traditional sportsbook that has been in business since 1999 (Gambling911.com actually had the pleasure of visiting their office the first week they set up shop that summer).
“Their customers represent an actual cross-section of the electorate,” remarked Payton O’Brien, Senior Editor at Gambling911.com. “It’s similar to polling, but with a financial incentive attached — these are people willing to put money behind their opinions and accept real financial risk.”
Prediction markets like Kalshi, by contrast, present themselves as financial exchanges for event contracts, meaning users are categorized as “traders,” not gamblers. The company operates under the oversight of the Commodity Futures Trading Commission (CFTC) as a regulated exchange.
Their customer base includes hedge funds, quantitative trading firms, market makers, arbitrage traders, and retail speculators. As a result, participants on these platforms do not necessarily reflect the broader electorate — particularly voters in Middle America or less politically engaged demographics. Instead, the user base can skew toward financially sophisticated traders and highly online political enthusiasts.
Paxton's jaw-dropping victory Tuesday night likely resulted in early general election betting on the Texas Senate race to move more in his direction.
Ahead of that victory, Democratic candidate James Talarico had been a -130 favorite versus the Republican candidate at even odds. BetOnline already had a sense it would be Paxton. By Wednesday morning, those odds had shifted to Paxton -125 and Talarico -105.
- T.C. Jackson, Gambling911.com
