John Cornyn tried to hand Biden a border deal.
Now he's watching Ken Paxton surge eight points ahead of him in the Texas Senate runoff – two days before voters decide.
Find out what Trump just just did to one of the most powerful Republicans in the Senate.
Trump Endorses Paxton: What He Actually Said About Cornyn
John Cornyn spent $135 million trying to hold his Senate seat – and Donald Trump erased it in one Truth Social post.
The moment Trump called Cornyn "late" on his 2024 endorsement, every Texas Republican voter understood exactly what that meant.
Now Ken Paxton holds a near double-digit lead heading into Tuesday's runoff, and betting markets give Cornyn about a 4% chance of survival.
Trump's May 19 Truth Social post didn't attack Cornyn viciously. It didn't have to. "John Cornyn is a good man, and I worked well with him, but he was not supportive of me when times were tough," Trump wrote. "John was very late in backing me."
That's it. That's the whole case.
Cornyn held off endorsing Trump's 2024 presidential bid until January of that year – only after Trump had already locked up Iowa and New Hampshire and the nomination was effectively over.
Paxton, by contrast, was one of just two elected officials who showed up at Trump's presidential campaign launch in 2022.
In a Republican primary, especially a runoff where only hardcore MAGA voters show up, that contrast doesn't just matter. It's the entire race.
https://x.com/TVNewsNow/status/2058709937732165756“>https://x.com/TVNewsNow/status/2058709937732165756
How the Texas Senate Primary Became the Most Expensive in State History
The day before Trump's endorsement, Cornyn's allies at Kalshi gave him a 37% chance of winning.
The day after, he had 7%.
That's not a shift. That's an implosion.
Cornyn entered this race with every institutional advantage imaginable. Twenty-two years of Senate seniority. Backing from Republican leadership. Outside groups alone poured over $60 million propping him up – part of a total $135 million spent across the race, making it the most expensive Senate primary in Texas history, second only to the 2022 Arizona race nationally.
Paxton had $5.9 million.
None of it mattered once Trump spoke.
And here's what Cornyn actually did with all that establishment muscle: in 2022, he negotiated a bipartisan gun safety bill with Senate Democrats while Paxton was standing next to Trump at Mar-a-Lago.
Your senator. Your Republican. Cutting gun deals with Chuck Schumer.
Texas gun owners didn't forget that. They just waited.
Why Cornyn's Electability Argument Collapsed
Cornyn's entire argument was electability. His pitch to Texas Republicans was essentially: "Paxton is too radioactive. I'm safer in November."
There's a factual basis for that concern. Paxton was impeached in 2023 by the GOP-dominated Texas House on 16 counts of alleged wrongdoing – the state Senate later acquitted him, but the damage was done.
But Republican primary voters don't take electability advice from senators who doubted Trump.
Paxton understood this perfectly. His stump speech opens with a challenge: name one thing Cornyn has actually accomplished. Then Paxton contrasts that record against his own – 13 years of suing the Biden administration, fighting left-wing organizations in court, and standing with Trump before it was popular.
"The MAGA agenda is dead under John Cornyn," Paxton said on Fox last week. "He kills it every time."
Paxton and the Senate Filibuster: What Changes When He Wins
This race was never just about a Senate seat.
Texas Republicans have been fighting this war for years – insurgents pushing out the old guard cycle after cycle. Trump just handed them the weapon to finish it.
The pattern is unmistakable. When Trump endorses in a Republican primary, prediction markets move 30, 40, sometimes 90 points overnight. That's not just popularity. That's a veto.
Cornyn ran the smartest possible establishment campaign by the old playbook. He outspent Paxton nearly 10-to-1 with outside help, locked up every institutional endorsement, and hammered electability nonstop.
He's going to lose by 10 points.
More importantly, the Senate is about to get a member who already promised to take a "sledgehammer" to the filibuster – the procedural shield Cornyn and his establishment friends have used for years to block conservative priorities, including Trump's SAVE America voter ID bill.
Cornyn protected the filibuster. Paxton is going to break it.
That's the difference between a senator who manages the MAGA agenda and one who actually delivers it.
Sources:
- "Trump endorses Ken Paxton in Texas Senate race ahead of runoff," CBS News, May 20, 2026.
- "Rallies, ad blitzes and a Trump endorsement: inside the final days of the Cornyn-Paxton runoff," Texas Tribune, May 23, 2026.
- "Texas GOP Odds of Losing to James Talarico Climb After Trump Backs Paxton," Newsweek, May 19, 2026.
- "Texas GOP runoff suddenly looks like a potential wipeout – according to prediction markets," May 24, 2026.
- "Texas Senate Odds: Paxton Leads Cornyn In Runoff," Covers.com, May 2026.
- "Cornyn and Paxton head to runoff in Texas GOP primary for U.S. Senate," Texas Public Radio, March 3, 2026.
