Senate Majority Leader John Thune said Tuesday he will continue supporting Sen. John Cornyn despite President Donald Trump endorsing Texas Attorney General Ken Paxton in one of the most closely watched Republican Senate primaries of the 2026 cycle.
Speaking to reporters following Trump’s endorsement announcement, Thune praised Cornyn as “a principled conservative” and an “effective senator” for Texas, signaling a rare split between Senate Republican leadership and the president.
“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 Trump formally endorsed Paxton on Truth Social, delivering a major boost to the Texas attorney general as he seeks to unseat Cornyn in the Republican runoff election.
In his endorsement, Trump criticized Cornyn for insufficient loyalty during politically difficult periods of his presidency.
“Ken Paxton has been a warrior for Texas values and for our America First agenda,” Trump wrote. He added that Cornyn “was not supportive of me when times were tough.”
The endorsement immediately intensified an already bitter and nationally significant Republican primary battle that has exposed growing tensions inside the GOP between establishment Senate Republicans and Trump-aligned populists.
Early voting in the runoff began Monday and continues through Friday, with Election Day set for May 26.
Despite the internal divisions, Thune expressed confidence Republicans would retain control of 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 would need a net gain of four seats to retake control of the chamber.
Several races, including contests in Maine, Michigan, and North Carolina, are currently viewed as highly competitive.
The Texas race has become particularly important because Democrats believe a bruising Republican runoff could weaken the eventual GOP nominee heading into the general election against Democratic candidate James Talarico.
Recent polling has suggested an unusually competitive general election environment in Texas. One survey released Monday reportedly showed both Cornyn and Paxton running roughly even with Talarico in hypothetical head-to-head matchups.
That possibility has alarmed some Republicans, particularly moderates concerned that Paxton’s legal controversies and polarizing political image could jeopardize a seat long considered safely Republican.
Sen. Lisa Murkowski openly criticized Trump’s endorsement Tuesday, warning it could backfire politically.
“I was supremely disappointed,” Murkowski said. “How does that help strengthen the president’s hand when we lose a state like Texas?”
Paxton has remained a dominant figure among Texas conservatives despite years of legal and political controversies, including securities fraud charges that were later resolved and an impeachment battle in the Texas legislature from which he was ultimately acquitted by the state Senate.
Trump allies have framed the race as a test of loyalty to the president and the broader America First movement, while Cornyn supporters argue the longtime senator offers stability, fundraising strength, and legislative experience critical for maintaining Republican control of the Senate.
Cornyn, who has served in the Senate since 2002 and previously chaired the National Republican Senatorial Committee, has longstanding ties to GOP leadership and donor networks in Washington. But critics on the right have increasingly portrayed him as part of the party establishment out of step with the Republican base.
Paxton has sought to capitalize on that frustration, presenting himself as a fighter aligned more closely with Trump’s populist agenda on immigration, election integrity, and federal power.
The runoff has also become a broader proxy battle over the future direction of Senate Republicans after Trump’s sweeping victories reshaped the party.
