ALLEN, Texas (AP) — President Donald Trump on Tuesday endorsed Texas Attorney General Ken Paxton, supercharging his effort to oust incumbent Sen. John Cornyn in a Republican primary runoff.

"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 on social media.

When news of the endorsement broke, Paxton supporters began cheering and dancing to "YMCA," a Trump campaign anthem, at an event in Allen, Texas, where the attorney general was scheduled to speak.

Paxton and Cornyn qualified for the May 26 runoff after a March 3 primary, while Rep. Wesley Hunt finished third and did not advance.

Although the four-term Cornyn has backed Trump's agenda in Washington, Paxton pitched himself as a political warrior for the Make America Great Again movement. Trump's endorsement puts him at odds with his party's establishment, which is convinced that Cornyn is the better candidate for November's general election. The Democrats nominated Texas State Rep. James Talarico as their candidate for Senate.

In response to Trump's endorsement, Talarico said in a statement that "it doesn't matter who wins this runoff. We already know who we're running against: the billionaire mega-donors and their corrupt political system."

Cornyn's campaign did not immediately respond to a request for comment. On Monday, the senator said he believed that Trump had decided not to weigh in with an endorsement.

"I think the president doesn't want to disappoint some of his own political base, and some of the Paxton people have been talking to him and encouraged him to support him, I think that was a bridge too far for the president so he's just opted to say out of the race," he said.

Cornyn also argued that Paxton is a liability in a general election, where Democrats hope to flip the seat blue, and "Ken Paxton would hand it to them on a silver platter."

Trump, in his social media post, said Cornyn was "a good man" but "he was not supportive of me when times were tough." He complained that "John was very late in backing me in what turned out to be a Historic Run for the Republican Nomination."

The runoff between Cornyn and Paxton had been shaping up as a bitter and expensive battle for the future of the Republican Party, and one that was diverting resources from other competitive races elsewhere in the country.

Trump frustrated some Republicans by declining to endorse earlier in the race. On the Friday before the March 3 primary, he said that he had "pretty much" decided whom to support — but declined to say who — when asked by reporters on a visit to Corpus Christi.

On the day after the primary, Trump promised to make an endorsement and said he would expect the candidate without his support to drop out. Paxton had said that he would not leave the race.

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Trump has had an at-times cool relationship with Cornyn, notably after the senator suggested in 2023 that Trump could not win the presidency again in 2024 and that his "time has passed him by."

Cornyn also was an early critic of Trump's plan for a border wall between the U.S. and Mexico — a project he now supports.

A former state attorney general and state Supreme Court judge, Cornyn was first elected to statewide office 36 years ago. His understated style and judge's temperament contrast with the fiery rhetoric of Trump and his Make America Great Again movement.

Cornyn has had support from Senate Republican leadership, including South Carolina Sen. Tim Scott, chairman of the National Republican Senatorial Committee, who warned that "it is a strong possibility we cannot hold Texas if John Cornyn is not our nominee."

Some Republican leaders have worried the party will need to spend much more money to defend the seat if Paxton is the nominee — money they could be spending on Senate races in more competitive states. Paxton was acquitted in a 2023 impeachment trial on corruption charges. He also reached a deal in 2024 to end a long-running securities fraud case.

Trump stoked the competition on Feb. 27 in Corpus Christi, noting there's "a little bit of a race," while acknowledging their attendance.

"We have a great attorney general, Ken Paxton. Where's Ken? Hi, Ken," Trump said. He continued, "And we have a great senator, John Cornyn. Hi, John."

"It's going to be an interesting one, right? They're both great people," he added.

Trump mentioned the third candidate, Hunt, after running through the long list of Texas lawmakers present.

"Another friend of mine who is doing very well, Wesley Hunt," he said. "Wesley Hunt, what a good job."

Beaumont reported from Des Moines, Iowa, and Bedayn reported from Austin, Texas.