5 Key Moments in the Cornyn-Paxton Texas Senate Runoff
Texas Republicans head to the polls Tuesday for one of the most consequential and bitterly contested Senate primary runoffs in the state’s history. Four-term incumbent Senator John Cornyn faces Attorney General Ken Paxton in a race that has consumed over $135 million in advertising, drawn a last-minute endorsement from President Donald Trump, and exposed deep fissures within the Texas Republican Party. Here are the five key moments that have defined the contest.
1. Paxton’s SAVE Act Gamble
In early March 2026, news leaked that President Trump was considering endorsing Cornyn, triggering a massive backlash from Paxton supporters. The attorney general responded with a political maneuver that analysts described as “really adept.” Paxton offered to consider dropping out of the race if the Senate passed the SAVE America Act — a voting restrictions bill at the top of Trump’s agenda that lacks the 60 votes needed to overcome a filibuster.
“By floating the idea of dropping out, and essentially making himself a martyr for the cause of voter integrity, with leverage that he did not have, he showed that he would go further for Trump than most other Republicans,” said Joshua Blank, research director at the Texas Politics Project. The move effectively neutralized Trump’s potential endorsement of Cornyn and positioned Paxton as the more loyal Trump ally.
2. Cornyn’s Filibuster Flip
In late March, Cornyn dropped his decades-long support of the legislative filibuster, expressing openness to reform in order to pass the SAVE America Act. The shift was widely seen as an attempt to match Paxton’s commitment to Trump’s agenda. According to the Texas Tribune, Cornyn’s change of heart came after Paxton had already seized the mantle of the most aggressive Trump ally in the race. But it wasn’t enough — Trump ultimately cited Paxton’s support for terminating the filibuster when he made his endorsement.
3. Trump’s Endorsement of Paxton
On May 19, 2026, just one week before Election Day, President Trump endorsed Ken Paxton, citing Paxton’s loyalty and Cornyn’s lack thereof “when times were tough.” The decision went against the advice of Senate Majority Leader John Thune and the Washington Republican establishment, which had spent tens of millions boosting Cornyn.
Senator Ted Cruz noted the endorsement’s significance: “Any observer will acknowledge that President Trump’s endorsement makes it significantly more likely that Ken Paxton wins. How much more likely, I don’t know.” The endorsement came late in the race, however, with much of the early vote already cast — roughly 621,000 Republican ballots by May 22.
4. The Record-Breaking Ad Blitz and Character Attacks
The runoff has been defined by an unprecedented advertising war. Over $135 million has been spent throughout the primary and runoff — one of the most expensive Senate primaries in U.S. history. Cornyn’s campaign spent heavily on ads attacking Paxton’s character, highlighting his 2023 impeachment by the Texas House, his long-running securities fraud indictment, and allegations of an extramarital affair. As the Dallas Morning News reported, the race “curdled into a sour political feud, marked by adultery attacks, corruption accusations and competing claims.”
Paxton’s ads focused on Cornyn’s 24-year tenure in Washington and past comments expressing skepticism about Trump’s border wall. “The MAGA agenda is dead under John Cornyn,” Paxton said on Fox News. “He kills it every time, just like the Republican Senate that he’s part of.”
5. The Runoff Electorate Dynamics
With opinions about both candidates “relatively calcified,” turnout has become the decisive factor. Runoff electorates tend to be smaller and more hardline, giving Paxton a structural advantage. Early voting data showed that 85% of runoff voters were returning from the March primary, with only 3% new voters.
“Runoff voters as a group — independent of demographics, of region — the primary runoff electorate is just skewing to the right, or towards Paxton anyway,” said Ross Hunt, a GOP operative and pollster uninvolved in the contest. Cornyn’s path to victory relies on expanding the electorate beyond the typical hardline runoff voter, but early data suggests that has been a challenge.
What’s at Stake
The winner will face Democratic nominee State Representative James Talarico in November. Democrats have not won a statewide race in Texas since 1994, and no Democratic Senate candidate has won since 1988. But changing demographics and recent close margins — Trump won Texas by only 6 points in 2024 — have Democrats increasingly optimistic.
The outcome will also signal whether Trump’s endorsement power remains decisive in intra-party battles and whether the GOP is shifting further toward the MAGA wing ahead of the 2026 midterms. As the Associated Press noted, the contest is “Trump’s next opportunity to purge the party of incumbents he views as insufficiently loyal.”
Polls close across Texas at 7 p.m. local time Tuesday, with results expected to begin flowing in shortly after.