Thune Breaks With Trump, Backs Cornyn After Paxton Endorsement

Senate Majority Leader John Thune said Tuesday he will continue backing Sen. John Cornyn, even after President Donald J. Trump endorsed Texas Attorney General Ken Paxton in one of the most closely watched Republican Senate primaries of the 2026 cycle.

Thune’s remarks marked a rare public split between Senate Republican leadership and President Trump, whose endorsement instantly reshaped the Texas runoff and gave Paxton a major boost among America First voters.

Speaking with reporters after Trump announced his support for Paxton, Thune defended Cornyn’s conservative record and said his position had not changed.

“Cornyn is a principled conservative. He is a very effective senator for the state of Texas,” Thune said.

“None of us can control what the president does. That doesn’t change the way I feel. I will continue to be supportive of Senator Cornyn in his re-election,” Thune added.

The comments came just hours after President Trump formally endorsed Paxton on Truth Social, throwing his weight behind the Texas attorney general as he seeks to unseat Cornyn in the Republican runoff.

In his endorsement, Trump praised Paxton as a loyal fighter for Texas and the America First movement.

“Ken Paxton has been a warrior for Texas values and for our America First agenda,” Trump wrote.

Trump also criticized Cornyn, saying the longtime senator “was not supportive of me when times were tough.”

The endorsement immediately escalated an already bitter primary battle and exposed the deeper fight taking place inside the Republican Party. On one side are Senate leadership figures and establishment-aligned Republicans who view Cornyn as a reliable conservative with experience and fundraising power. On the other side are Trump-aligned populists who see Paxton as a fighter more closely connected to the grassroots base.

Early voting in the runoff began Monday and continues through Friday, with Election Day set for May 26.

Despite the division, Thune insisted Republicans remain well positioned to hold the Senate in November.

“I’m very confident we’ll hang on — and maybe even expand the majority of the United States Senate,” Thune said.

Republicans currently hold a six-seat Senate majority. Democrats need a net gain of four seats to retake the chamber, and competitive races in states such as Maine, Michigan, and North Carolina are already drawing national attention.

Texas has become especially significant because Democrats believe a bruising Republican runoff could weaken the eventual nominee before the general election against Democrat James Talarico.

Recent polling has suggested the general election could be more competitive than Republicans would like. One survey released Monday reportedly showed both Cornyn and Paxton running roughly even with Talarico in hypothetical matchups.

That has made some Republicans nervous, particularly moderates who worry Paxton’s political and legal controversies could put a seat long considered safely Republican into play.

Sen. Lisa Murkowski criticized Trump’s endorsement Tuesday and warned it could hurt the party’s chances.

“I was supremely disappointed,” Murkowski said. “How does that help strengthen the president’s hand when we lose a state like Texas?”

Paxton, however, remains a powerful figure among Texas conservatives. Despite years of legal and political battles, including securities fraud charges that were later resolved and an impeachment fight in the Texas legislature that ended with his acquittal in the state Senate, he has maintained strong support from the Republican base.

Trump allies have cast the race as a test of loyalty to President Trump and the America First agenda. To them, Paxton represents the kind of conservative fighter willing to challenge Washington, confront federal power, defend election integrity, and take a hard line on immigration.

Cornyn’s supporters argue that the veteran senator brings stability, legislative experience, and the fundraising network needed to keep Texas safely in Republican hands.

Cornyn has served in the Senate since 2002 and previously chaired the National Republican Senatorial Committee. His long record gives him deep ties to GOP leadership and donor networks, but it has also made him a target for conservatives who believe the party establishment has grown too comfortable in Washington.

Paxton has leaned into that frustration, presenting himself as the candidate more closely aligned with President Trump’s populist movement and the conservative voters who have transformed the Republican Party.

The runoff is now more than a Texas Senate race. It has become a proxy battle over the future of Senate Republicans, the power of Trump’s endorsement, and whether GOP voters want steady establishment experience or a more aggressive America First warrior in Washington.