Texas GOP Senate runoff pits Cornyn vs. Paxton in Trump-backed showdown

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Texas voters will hold their second attempt to nominate a Republican candidate for U.S. Senate in a primary runoff election on Tuesday, the electoral version of the Texas two-step, after the March 3 contest set up a head-to-head matchup. John Cornyn, the four-term incumbent and top vote-getter in March, will face state Attorney General Ken Paxton, who finished second and received President Donald Trump’s endorsement on May 19. The runoff also arrives alongside primary runoffs in more than a dozen congressional districts and state contests for lieutenant governor, attorney general and other offices.

Cornyn and Paxton reached the Tuesday runoff after Cornyn led the March 3 vote count but “strong showings” by two GOP challengers forced the incumbent into a head-to-head matchup with Paxton. The field narrowed again in the runoff so that voters would decide which Republican will appear on the November ballot.

The contest is also tied to Trump’s role in reshaping the party’s slate, as the AP Decision Notes described it as the president’s next opportunity to “purge the party of incumbents he views as insufficiently loyal to him and his agenda.” At the same time, the notes said Trump’s endorsement of Paxton did not include the kind of direct excoriation he has used with Republican incumbents in Indiana, Louisiana and Kentucky, and it highlighted a distinction in Trump’s remarks.

Trump’s endorsement for Paxton came with a contrast: Trump told voters that Cornyn “was not supportive of me when times were tough,” while Trump had appeared open to endorsing Cornyn following the March primary. The notes also said Cornyn had been critical of Trump ahead of the president’s 2024 campaign. With much of the Texas primary campaign framed around candidates’ loyalty to Trump, the AP Decision Notes said rural counties with the strongest Trump support could become decisive.

In an analysis of the March primary results by county support levels, the AP Decision Notes said Paxton beat Cornyn in counties Trump carried with 80% or more of the vote, by 45% to 40%, while Cornyn performed better than Paxton in the rest of the state. In counties Trump carried with between 50% and 80% of the vote, Cornyn received about 42% of the vote, edging Paxton by about a percentage point. The notes added that in 12 counties that Democrat Kamala Harris carried in 2024, Republican primary voters preferred Cornyn 44% to 40%, and said those counties made up about 25% of the overall primary vote—larger than the share of Trump’s 80%-plus counties.

Whoever wins Tuesday’s Republican runoff will face Democrat James Talarico in the general election, according to the AP Decision Notes. The notes also pointed to how rare incumbent losses have been in Texas Senate primaries in recent history, saying only two incumbent U.S. senators from Texas have lost a primary in the last 100 years.

The Tuesday election includes more than the Senate runoff. In the new congressional map drawn by Republicans in 2025 at Trump’s urging to maintain control of the U.S. House, the AP notes said some Democratic primary runoffs will also reflect redrawn districts, including an 18th Congressional District contest between U.S. Reps. Christian Menefee and Al Green, and a 33rd Congressional District matchup between U.S. Rep. Julie Johnson and her predecessor, former U.S. Rep. Colin Allred.

For voters and for viewers tracking results, the AP Decision Team laid out key logistics for the night. Polls close statewide at 7 p.m. local time, which is 8 p.m. ET for most of Texas and 9 p.m. ET for the westernmost areas on Mountain time, according to the notes. As of Thursday, the AP Decision Notes said about 621,000 Republican primary ballots and about 262,000 Democratic primary ballots had already been cast in Tuesday’s election, and it noted that counties tend to release early and absentee results in the first vote update of the night.

The AP Decision Notes also spelled out runoff voting rules: voters who did not participate in a party primary on March 3 may vote in the runoff for either party, but voters who did cast a ballot in a party primary may vote only in the runoff of the same party. The notes said non-partisan primary voters can choose either party’s runoff. It also described baseline turnout from the March primary, saying there were nearly 19 million registered voters in Texas as of March 3, with about 2.2 million Republican primary votes and about 2.3 million Democratic primary votes cast in March.

The AP Decision Notes included expectations about how voting and counting typically unfold on election night. It said about 63% of the vote in the March 3 Republican primary was cast before primary day, and that in the U.S. Senate primary in March the AP first reported results at 8 p.m. ET as polls closed in most of the state, with 75% of the vote counted by 11:39 p.m. ET. It said results were released continuously until about 5:58 a.m. ET, with about 98% of the total vote counted, and it reiterated that the AP would declare a winner only when it is determined there is no scenario in which a trailing candidate could close the gap.