With just days until Texas’ primary, Republicans in Washington are growing more alarmed that their increasingly vicious intraparty contest could cost them a must-win Senate seat.

Sen. John Cornyn appears to be headed to an expensive and nasty 10-week runoff against Texas Attorney General Ken Paxton, with a strong chance that Paxton wins the nomination even after national Republicans spent months airing his dirty laundry all over the Texas airwaves in an effort to boost Cornyn. 

“Honestly, if you look at the polling in a general election setting, I don’t think it’s outside the realm of possibility that the seat [flips], depending on who the Democrats nominate,” said Senate Majority Leader John Thune, when asked about the possibility that Republicans could lose the race if Cornyn, who he endorsed, is not the party’s nominee.

If Cornyn loses the primary, Senate Republicans worry they could be forced to spend hundreds of millions of dollars that could otherwise go toward key battleground races in expensive states like North Carolina, Georgia or Michigan, complicating their path toward holding Senate control.

Republicans have already spent nearly $100 million on TV advertising in the primary, which also includes Rep. Wesley Hunt (R-Texas), according to data from AdImpact. And Cornyn launched new ads this week, with support from the National Republican Senatorial Committee, that hammer Paxton in ways that could hurt him in the general election too: highlighting his messy ongoing divorce and accusations of corruption and calling Paxton a “wife-cheater and fraud.”

But those attacks haven’t stopped Paxton, a MAGA hero more aligned with the party base who has been bolstered by positive polling and a wave of grassroots enthusiasm.

“All signs indicate that Paxton probably finishes first,” a Washington GOP operative close to Cornyn told Blue Light News granted anonymity to candidly discuss the race. “We’re just hoping the gap is close enough the narrative isn’t ‘Paxton kicked the crap out of Cornyn.’”

Paxton attended the president’s State of the Union address Tuesday night as a guest of Rep. Troy Nehls (R-Texas), who called warnings of an expensive general election a “scare tactic.”

“What you’re doing now is you’re telling Texas you can’t elect Ken Paxton, not because you do a better job than me, but it’ll cost too much to win it,” said Nehls. “What a desperate attempt to convince voters to not vote for Ken Paxton because it could cost too much money in November. That’s ridiculous.”

Paxton is predicting a massive victory. Speaking with reporters after a campaign rally in the Houston suburbs last Friday, he suggested he may win the race outright and avoid a runoff.

Both Paxton and Cornyn allies have been running ads attacking Hunt in recent days, a sign either that they see a chance that Hunt could edge Cornyn for a spot in the runoff — or that Paxton could win outright.

If the race does extend until the end of May, Paxton said he doesn’t intend to change his strategy.

“It’ll be grassroots, just like it always has been, and we’ll be out trying to compete,” Paxton said. “Obviously, [Cornyn] has got a lot of money, D.C. money. I don’t have that money. We’ll have our money from Texas.”

A spokesperson for Hunt said the congressman told NRSC chair Sen. Tim Scott last year before he got into the race that Cornyn was going to lose, but “Washington ignored it.” They also warned that Paxton could be vulnerable in the general election.

“If Senate Republicans lose the majority, it will be because the NRSC failed to plan for the future and chose to spend a record-breaking sum meddling in a Republican primary in Texas, of all places, where the GOP nominee is almost always favored to win,” the spokesperson said. “That’s malpractice.”

Republican Party officials and Senate GOP leaders think Cornyn has a far better chance than Paxton of staving off a Democratic challenger in the general election. When asked for comment on the race, the NRSC pointed to a memo it circulated to donors earlier this month that said that “John Cornyn is the only Republican candidate who reliably wins a general election matchup,” and warned “Paxton puts this seat at risk.”

“We have to be prepared to spend there, and that’s a very different scenario if Cornyn’s the nominee,” Thune said. “He is by far, I think, the best candidate on the ballot in a general election, not only for the Senate, but also for down-ballot races in the House that could be impacted by the Senate race too.”

The polls bear that out. The NRSC released polling toplines showing Cornyn leading state Rep. James Talarico by 3 points and Rep. Jasmine Crockett (D-Texas) by 7 points in general-election matchups. Paxton would trail Talarico by 3 points and lead Crockett by just 1 point. Nonpartisan public polls have found similar numbers.

A Democrat has not won a U.S. Senate election in Texas since 1988.

Rep. Monica De La Cruz (R-Texas), who hasn’t made an endorsement in the race, said she hopes the Republican primary avoids a runoff. “We’ve got to keep Texas red,” she said. “That is not a choice, and so the faster we can get someone in place, the better it is for all Texans.”

During a Fox News appearance Monday, Cornyn said he anticipates he will face Paxton in a runoff and warned that a Paxton victory would give Democrats a boost in November.

“Unfortunately, the attorney general has got so much baggage and corruption in his wake that he will jeopardize our chances of keeping this seat red in November,” Cornyn said. “I believe that I can help President Trump in [the] end of his second term by not only winning this race, but bringing along some of these congressmen who are running in these five new congressional seats. Ken Paxton jeopardizes all of that.”

Paxton has led or been in a statistical tie with Cornyn in nearly every primary poll since launching his bid in April of last year, despite campaigning minimally and spending a small fraction compared with Cornyn’s war chest. It’s a testament to Paxton’s status as an aggressive MAGA figure in Texas, a reputation he has forged while serving as Texas’ top lawyer for a decade. Paxton used the power of his office to stoke the culture wars in court, like suing to overturn the 2020 election and defending the state’s strict abortion ban.

Dave Carney, an adviser to Texas Gov. Greg Abbott, predicted that Cornyn and Paxton will face off in a runoff, where he suggested Paxton would have the edge. The most conservative candidate tends to win because they often have the most driven supporters in low-turnout primary runoff elections.

“They have to run real campaigns, both of them, they got to model their voters and turn them out,” said Carney.

To date, Trump has resisted making an endorsement in the primary. “I’m friendly with all of them,” he said earlier this month. “I like all of them, all three.”

Thune and other Senate Republicans for months privately lobbied to get Trump to endorse Cornyn, believing he would be the most formidable candidate in the general election. Thune has been careful not to predict what Trump will do in the future. Some top Trump political aides are working on Cornyn’s campaign — but the president has a longstanding relationship with Paxton. There is lingering skepticism in and outside of the Capitol that Trump would endorse Cornyn if the senator comes in second heading into the runoff.

Trump is scheduled to make an appearance in Corpus Christi on Friday to deliver a speech on the economy. A White House aide, granted anonymity to speak freely, said the president will not endorse at the event. The White House hasn’t announced if any of the GOP Senate candidates will join Trump on the trip.

Top GOP donors, too, worry that the party is burning money — and that Paxton still has the upper hand in spite of the huge spending against him, with some concerned about an outright Paxton win.

“Nobody truly knows what is going to happen based on the polling,” said one GOP donor. “There is a scenario [where] Cornyn doesn’t make it into a runoff. But even if he does, a runoff with Paxton will be very tough because of [the] low number of voters who turn out — most of whom are very conservative and viewed as Paxton voters.”

The person added that there is “frustration from everyone that Trump lets this happen by not endorsing.”

Another GOP donor said there’s “not a lot of cautious optimism” among donors that Cornyn will even make it to a runoff. “It’s going down to the wire,” the donor lamented.

Lisa Kashinsky contributed reporting.