By Elizabeth Findell, Meridith McGraw and Natalie Andrews

President Trump on Tuesday endorsed Texas Attorney General Ken Paxton for Senate over incumbent Sen. John Cornyn, throwing an 11th-hour curveball into a vicious and tightly contested Republican primary.

"Ken is a true MAGA Warrior who has ALWAYS delivered for Texas, and will continue to do so in the United States Senate," Trump wrote in a lengthy Truth Social post. "Ken Paxton has gone through a lot, in many cases, very unfairly, but he is a Fighter, and knows how to WIN. Our Country needs Fighters, and also Loyalty to the Cause of Greatness."

Trump called Sen. John Cornyn a "good man" but added, "he was not supportive of me when times were tough." He also said Cornyn "was very late in backing" his 2024 run for president.

Trump's endorsement comes a day after early voting began in the May 26 primary runoff. Cornyn, who has held the office since 2002, faces a fierce intraparty challenge from Paxton, a MAGA warrior who accused him of not being firm enough in his backing of Trump. Paxton has held an edge with far-right base voters, while Cornyn has had backup -- and significant fundraising advantages -- from old-school Republican stalwarts. The pair advanced to the runoff after receiving the most votes in a three-way March primary.

Paxton posted on X just after the announcement that he was honored to have the endorsement. "No one has ever fought harder for the American people than President Trump, and I look forward to championing his America First agenda in the Senate!," Paxton wrote.

In a post on X after, Cornyn said he has worked closely with Trump in both his terms and voted with him more than 99% of the time. "He has consistently called me a friend in this race," Cornyn wrote. "It is now time for Texas Republican voters to decide if they want a strong nominee to help our GOP."

The president has been flexing his political muscles in the GOP primary elections, seeking to keep Republicans in line and purging the party of critics. He successfully ended the re-election bid of Sen. Bill Cassidy (R., La.) on Saturday and is seeking to take out Rep. Thomas Massie (R., Ky.) in voting Tuesday.

Republicans currently have a 53-47 majority in the Senate, and are counting on retaining Texas to keep their majority. But the race has been a source of anxiety for Republicans.

National GOP groups and Cornyn supporters fear that nominating scandal-prone Paxton could hand a win to Democratic nominee James Talarico, whom they see as a formidable general election candidate. Others have raised alarms about the ugliness of the primary overall, saying that if even a fraction of Cornyn or Paxton voters are unwilling to vote for the other, Talarico could win.

"I think that this puts that seat in jeopardy," Sen. Lisa Murkowski (R., Alaska) said of Trump's decision to endorse Paxton, adding that she is "supremely disappointed."

Asked by reporters for his reaction to Trump's endorsement, Senate Majority Leader John Thune (R., S.D.) said: "It's his decision." The Senate GOP's campaign arm, the National Republican Senatorial Committee, had previously endorsed Cornyn in the race.

Cornyn and Paxton have been lobbying for Trump's support for months, while Cornyn allies in Washington have made repeated arguments to Trump that he is better to protect Republicans' majority in November. Trump was set to endorse Cornyn in March, people close to both campaigns said, after writing on Truth Social that their battle "MUST STOP NOW!"

But Trump held off on the endorsement after Paxton took to social media to pressure Cornyn to push the Senate to pass one of Trump's legislative priorities: a voting bill dubbed the SAVE America Act. Cornyn then reversed his longstanding defense of the Senate's filibuster rule that requires 60 votes to advance most legislation, siding with Trump over Senate leaders in an attempt to ease the bill's passage.

Vice President JD Vance told reporters on Tuesday he has known Cornyn for a long time, but added, "unfortunately, when it really counted, Ken Paxton was there for the country and there for the president."

Many Texas political observers initially gave Paxton the edge in the race. He was ahead in polls before the March primary and low-turnout runoffs typically favor more extreme candidates. But Cornyn eclipsed Paxton in fundraising and spending and overperformed expectations in the March contest, winning 42% of votes to Paxton's 41%. More recent polls have shown the runoff to be close. Results from a recent University of Houston poll of likely runoff voters were 48% for Paxton, 45% for Cornyn and 7% undecided.

Paxton faces a significant fundraising gap. Talarico has raised more than $40.2 million so far, according to FEC records, compared with Paxton, who has raised $7.6 million.

Talarico issued a statement after the endorsement saying it doesn't matter who wins the primary. "We already know who we're running against: the billionaire megadonors and their corrupt political system," he said.

Write to Elizabeth Findell at elizabeth.findell@wsj.com, Meridith McGraw at Meridith.McGraw@WSJ.com and Natalie Andrews at natalie.andrews@wsj.com

(END) Dow Jones Newswires

May 19, 2026 14:17 ET (18:17 GMT)

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