Ken Paxton entered the final hours before Tuesday's Texas GOP Senate runoff with a massive edge on the prediction market Kalshi, which pegged the state attorney general's chances at 95.6 percent as of Sunday afternoon, a figure that dwarfs the 4.4 percent assigned to four-term incumbent Sen. John Cornyn.
The numbers moved fast. On Monday morning, before President Trump formally endorsed Paxton, Kalshi had the attorney general at 63.7 percent and Cornyn at 37.2 percent. By Sunday, the gap had become a chasm, as The Hill reported. Whatever residual hope Cornyn's allies had of a late comeback now rests on the slim possibility that prediction-market bettors have the race wrong.
That possibility exists. But the trajectory tells a story that traditional polls had already hinted at: a University of Houston Hobby School of Public Affairs survey conducted April 28 to May 1 found 48 percent of 1,000 likely voters backing Paxton, 45 percent backing Cornyn, and 7 percent undecided. The Trump endorsement appears to have turned a tight race into a rout, at least in the eyes of the market.
Trump's endorsement landed Monday morning and carried the blunt language voters have come to expect. He called Paxton a "true MAGA warrior" and said Cornyn had not been supportive of him "when times were tough."
That second line cuts deeper than it might sound. Cornyn said in 2023 that Trump's "time has passed him by." For a senator seeking renomination in a state where Trump remains the dominant force in Republican politics, those five words may prove to be the most expensive sentence of his career.
Paxton, for his part, filed litigation supporting Trump's efforts to challenge the 2020 presidential election results, a move that cemented his standing with the MAGA base and made him a target for the party's establishment wing. The contrast between the two candidates' postures toward Trump could hardly be sharper.
The pattern of Trump-aligned challengers toppling incumbent senators has become familiar. In Louisiana, Sen. Bill Cassidy finished third in his own GOP primary after Trump-backed candidates shut him out entirely. Cornyn now risks a similar fate in a state where no Democrat has won a Senate race since Lloyd Bentsen in 1988.
The senator spent the final stretch warning Republicans that nominating Paxton would hand Democrats a general-election opening. At a Friday event in Corpus Christi, the same day early voting ended, Cornyn told supporters that Paxton "will be an albatross around the neck of all of our candidates" if he becomes the nominee.
It is a familiar argument from establishment incumbents facing populist challengers: electability. Senate Republicans have echoed Cornyn's concern, expressing fear that Paxton would be a weaker general-election candidate against Democratic nominee James Talarico, a state representative.
But the electability case requires voters to believe Texas is genuinely competitive in a Senate race. The last Democrat to carry the state in a presidential election was Jimmy Carter in 1976. That is nearly half a century of Republican dominance. Telling Texas GOP primary voters they need to pick the "safe" candidate in a state this red is a tough sell, especially when the alternative carries a presidential endorsement.
Cornyn appeared on NewsNation's "The Hill Sunday" program and was asked whether he would support Paxton if the attorney general wins the runoff. His answer was notably noncommittal. He told host Chris Stirewalt:
"I expect to be the nominee of the party, so I don't expect to ever have to deal with that."
That kind of answer rarely ages well. It signals either genuine confidence or a refusal to confront the obvious, and the prediction markets suggest which interpretation is more likely.
While Cornyn was still making his case against Paxton's viability, Paxton was already acting like the nominee. The attorney general posted on X that his campaign had changed its television ad strategy "to ensure our campaign ends on a positive note" and to shift focus toward defeating Talarico in November. He called on Cornyn "to do the same for the good of our party."
The move was tactically shrewd. By pulling negative ads and pivoting to the general election, Paxton positioned himself as the candidate looking forward while Cornyn remained stuck arguing about November risks. It also put Cornyn in an awkward spot: continuing to attack a fellow Republican who has already extended an olive branch.
The broader dynamic within the GOP has been playing out across multiple states. Incumbent senators who distanced themselves from Trump have faced escalating backlash from the base, and the institutional party has struggled to protect them.
Prediction markets are not polls, and they are not election results. But they aggregate real money from bettors who have a financial incentive to be right, which gives them a different kind of credibility than surveys conducted weeks before election day.
The Kalshi shift from 63.7 percent to 95.6 percent in a matter of days tracks with the Trump endorsement timeline. Before Trump weighed in, the race looked competitive. After, the market priced in a near-certain Paxton victory.
The University of Houston poll, conducted before the endorsement, showed a three-point Paxton lead with a meaningful undecided bloc. In a low-turnout runoff, that 7 percent of undecided voters could have broken either way. Trump's endorsement likely collapsed much of that uncertainty in Paxton's direction.
Cornyn's own political evolution has not helped his cause. The senator shifted his position on Senate rules in recent months, backing changes to push legislation through, a move that seemed calibrated to align himself more closely with Trump's priorities. But for many primary voters, late conversions carry less weight than consistent loyalty.
Senate Republicans' anxiety about a Paxton nomination centers on Talarico, the Democratic state representative who would face the GOP winner in November. The fear is that Paxton's combative profile and legal history give Democrats a better target than the more conventional Cornyn.
That concern is not baseless in the abstract. But it collides with Texas electoral reality. The state has not sent a Democrat to the Senate in nearly four decades. Even in the closest recent statewide race, Beto O'Rourke's 2018 challenge to Sen. Ted Cruz, the Republican won. Arguing that Paxton would somehow lose a state this deep red requires a theory of the case that goes beyond generic electability worries.
The broader lesson from recent GOP primaries is that voters have stopped deferring to Washington's judgment about who can win. Electoral outcomes do not always follow establishment expectations, and Republican primary voters have shown repeatedly that they value alignment with Trump over institutional credentials.
Strip away the prediction-market numbers and the polling crosstabs, and this runoff comes down to a simple question: Which candidate stood with Trump when it mattered?
Paxton's answer is straightforward. He filed legal challenges on Trump's behalf after 2020 and has positioned himself as a MAGA loyalist throughout his tenure as attorney general. Cornyn's record is more complicated. A four-term senator with deep institutional ties, he made his 2023 comment about Trump's political relevance at a moment when many in the party thought the former president's grip was loosening. It wasn't.
Now Cornyn faces the consequences of that miscalculation. A 95.6 percent prediction-market probability is not a guarantee, but it is a verdict from people willing to put money behind their judgment. And that judgment says Texas Republican voters know exactly who they want.
In politics, timing is everything. Cornyn chose the wrong moment to bet against Trump, and Texas voters appear ready to make him pay for it.