As Trump keeps Texas guessing, neither Cornyn nor Paxton backs down from Republican Senate runoff

President Donald Trump has said he plans to endorse one of the candidates in the Republican Senate runoff in Texas, but Tuesday is the last chance for either to withdraw from the ballot and fulfill the party's hope of avoiding more than two months of bitter and costly campaigning.

Neither incumbent Sen. John Cornyn or state Attorney General Ken Paxton have shown any signs of bowing out, instead launching new advertisements criticizing each other.

Trump told NBC News on Saturday that he thinks he’ll bestow an endorsement this week. But it's already been two weeks since he originally promised to back a candidate “soon" and urge the one without his support to drop out of the race “for the good of the Party."

Cornyn finished ahead of Paxton in the March 3 primary, although he didn't secure the majority needed to avoid a runoff.

Asked about the chance of Cornyn dropping out, campaign spokesman Matt Mackowiak said “of course not” and "we’ve already started our campaign.”

An ad released Tuesday by Cornyn's campaign highlighted allegations that Paxton had an affair and his impeachment by Texas' Republican-controlled House. Paxton was later acquitted and denied corruption accusations. Another ad framed some of the same accusations as Paxton violating the Ten Commandments.

As to whether Paxton plans to step down, campaign spokesman Nick Maddux declined to comment. But the candidate introduced a new attack ad against Cornyn on Friday and is scheduled to speak this month at the Conservative Political Action Committee’s annual convention, hardly the signs of a candidate eyeing the exit.

The ad is a series of news clips highlighting Cornyn's past critiques of Trump, including over the president's false statements that the 2020 election was stolen, and frames Paxton as the MAGA-aligned candidate.

A pro-Paxton super PAC has also sought to catch Trump’s attention by airing an ad with the same messaging in the West Palm Beach, Florida, market, which includes Trump’s resort home, Mar-a-Lago.

But Cornyn, a more traditional Republican, isn't retreating from the fight over who's the better MAGA adherent: the first sentence on his website is “Cornyn votes with President Trump 99% of the time."

Trump told NBC News that he likes “both candidates very much" and believes that either could beat the Democratic nominee, state Rep. James Talarico, in the general election.

While Cornyn came out slightly ahead of Paxton in the primary, the second round of voting could favor the attorney general since runoffs typically draw a more conservative, activist corner of the Republican Party.

"Cornyn has always had a weakness with the most conservative voters in the electorate," said Joshua Blank, director of research for the Texas Political Project at the University of Texas, Austin, which conducts statewide polls.

Still, he added, Cornyn's primary campaign appeared to offset at least part of that disadvantage and “illustrate for the Republican primary electorate what kinds of vulnerabilities that Ken Paxton has.”

The ads, however, matter less in a runoff contest, said veteran Texas Republican strategist Dave Carney. The smaller, more concentrated electorate puts an emphasis on identifying individual voters, contacting them directly through digital advertising and texts, he said.

“Whoever has good data and knows who their supporters are and turns them out will win,” he said.