President Donald Trump endorsed Texas Attorney General Ken Paxton’s primary challenge against Sen. John Cornyn (R-TX) on Tuesday, dealing a significant blow to Cornyn’s bid for a fifth term.

Trump announced the Paxton endorsement in a post on Truth Social a week before the runoff election, writing that while Cornyn “is a good man,” the senator was insufficiently “supportive of me when times were tough.” He pointed to Cornyn’s late backing of his presidential bids and his aversion to terminating the filibuster in the Senate in order to pass the president’s Save America Act. 

The president argued that Paxton, on the other hand, “is a true MAGA warrior who has ALWAYS delivered” for Texans, calling him “someone who has always been extremely loyal to me and our AMAZING MAGA MOVEMENT.”

The endorsement makes Paxton the odds-on favorite to win the Republican nomination, given Trump’s track record of success with his endorsed candidates in primaries. Cornyn narrowly finished ahead of Paxton in the first round of balloting in March with 42% of the vote, while Paxton received 41%. 

If Paxton wins the May 26 runoff, Democrats plan to invest millions behind their nominee, state Rep. James Talarico, who is trying to become the first Democrat to win a Senate seat in Texas since 1988. General election polling indicates that a matchup between Talarico and Paxton — who carries significant legal and ethical baggage — would be highly competitive. 

Sen. Lindsey Graham (R-SC) told reporters Tuesday that he thought the race would be three times more expensive with Paxton as the nominee. “You don’t have to be a rocket scientist to figure out the pathway for Paxton is there, but it’s more uphill.” Graham said.

Paxton thanked the president for his endorsement on X, saying “he look[s] forward to championing his American First agenda in the Senate.” In March, Paxton said that he would consider withdrawing from the race if Senate GOP leadership, who were lobbying the president to endorse Cornyn, agreed to get rid of the filibuster to pass the Save America Act, Trump’s election security bill. GOP leadership did not seriously consider Paxton’s offer, two sources familiar with the matter told JI.

Cornyn, in a statement, said that he has  “worked closely with President Trump through both of his presidential terms and voted with him more than 99% of the time,” claiming Trump has “consistently called me a friend in this race.” 

“It is now time for Texas Republican voters to decide if they want a strong nominee to help our GOP candidates down ballot and defeat [Democratic state. Rep James] Talarico in November, or a weak nominee who jeopardizes everything we care about,” Cornyn continued.

Cornyn, who was first elected in 2002, warned in an interview with Jewish Insider in February that the GOP is at risk of being overrun by extremists if prominent conservatives continue to align themselves with fringe figures who espouse antisemitic views, and attacked Paxton for appearing on Steve Bannon’s podcast.

“To maintain the integrity of conservatives, that’s why it’s so important to call out and to cut out some of these cancers that I think ultimately would result in the failure of the conservative movement,” Cornyn said.

“I know Ken Paxton regularly goes on Bannon’s ‘War Room’ podcast, and it’s something that should be alarming to Texas voters. People like that I don’t think are what I would call conservatives.”