Texas Senate GOP Race Tightens as Trump Skips Key Endorsement Deadline

President Donald Trump let a key deadline pass without endorsing either incumbent Sen. John Cornyn or Texas Attorney General Ken Paxton in the lead-up to the Texas GOP Senate primary runoff May 26.

March 17 was the deadline for candidates to withdraw from the race. Cornyn and Paxton advanced from the initial March 3 primary election, where Cornyn topped the list at approximately 35% and Paxton second at about 30%, forcing the runoff under Texas rules requiring 50% to win. 

Trump had pledged after the primary to back a candidate and urge the other to quit, but held off. Prediction markets reacted instantly to the news, with volume spiking as traders bet on endorsement fallout and attack ad escalations.

The race has been personal and historically expensive, according to the New York Times, as the pair vie to take on Democratic upstart Texas State Rep. James Talarico in November.

Platforms pour in

Polymarket‘s Texas Republican Senate Primary Winner market is a popular election market with $12.2 million total volume. Cornyn is currently sitting at 62%, with $2.6 million in volume, while Paxton’s clocking at 39% on $3.8 million in volume. 

Kalshi‘s related Texas Senate GOP markets are nearing $11 million, with direct runoff odds nearly mirroring Polymarket at 60% Cornyn, 40% Paxton.

Platforms align on Cornyn’s incumbency edge and strong fundraising. But Paxton’s Trump-base pull keeps it tight. Prior to March 3, polls largely had Paxton edging out Cornyn by approximately 4%. 

Where do Texas primary markets go from here?

The markets seem to be pricing Cornyn’s general strength despite Paxton’s MAGA base fire. If Trump stays silent, money will likely continue a steady grind to Cornyn, but a late endorsement could flip the market fast. 

On Polymarket’s runoff margin of victory market, the most‑traded outcome remains “Cornyn 3–6%,” but pricing on narrower Cornyn wins and Paxton squeakers tightened as the no‑endorsement news broke, reinforcing the view of a razor‑thin race rather than a blowout. Kalshi’s margin of victory market has low volume so far, but Cornyn by 0-5% has the highest odds so far.

For now, the signal is less about who wins than how close it will be. Prediction markets are converging on a high‑turnout, single‑digit contest that neither candidate can lock up without a late break in news or a Trump endorsement.

Regardless of who wins between Cornyn and Paxton, the Texas Senate winner market, with $1.7 million in volume, has the Republican candidate at 57% over Talarico. That comes as Public Policy Polling is tracking Talarico as a slight favorite over either Republican candidate.

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