The last major poll before Tuesday’s Texas Republican Senate runoff shows Ken Paxton with a clear lead over Sen. John Cornyn. The Quantus Insights survey, conducted May 21-23 among 1,018 likely GOP runoff voters, puts Paxton at 52.7% and Cornyn at 43.4%, with 3.9% still undecided. The effective sample size was 936, with a weighted margin of error of roughly 3.5 points. That nine-point gap is remarkable given where this race started. Cornyn narrowly finished first in the March primary by just 1.5 points, forcing the runoff in the first place. Something shifted the race, and the obvious factor is President Trump’s endorsement of Paxton. As Trending Politics noted, the Quantus survey found that awareness of President Trump’s endorsement was nearly universal among likely runoff voters. Most respondents said the endorsement did not change their vote. Among the voters it did move, the shift broke heavily in Paxton’s direction. Another election account posted the same exact Quantus topline from the final survey window: Quantus poll | 5/21-5/23 LV US Senate Texas Republican primary 2026 Ken Paxton 52.7%John Cornyn 43.4% (incumbent) — Politics & Poll Tracker (@PollTracker2024) May 25, 2026 That tracks with what you would expect in a Republican-only runoff where President Trump’s word still carries enormous weight. According to Quantus Insights, Paxton’s lead appeared consistent across multiple demographic and geographic cross-tabs within the likely voter universe. Cornyn, a three-term incumbent and former Senate Majority Whip, has been a fixture of the Texas GOP establishment for two decades. He bet that his seniority and institutional relationships would carry him through a runoff against Paxton, who served as Texas Attorney General before mounting this challenge. That bet is not looking strong heading into Tuesday. A poll is not an election result, and 3.9% of voters remain undecided with the margin of error at 3.5 points. Turnout in runoff elections is notoriously difficult to predict, and both campaigns will be working to get their voters to the polls on Tuesday. But the direction of the numbers is unmistakable. Texas Republicans are heading to the polls to answer a straightforward question: does this Senate seat stay with the old guard, or does it move further into President Trump’s America First lane? If the Quantus numbers are anywhere close to accurate, GOP primary voters have already made up their minds. 270toWin spotlighted the rounded topline as the race hit its final stretch: Texas Senate runoff poll conducted after Trump endorsement of Paxton just published by @QuantusInsights Paxton 53%, Cornyn 43%https://t.co/QVwbQnIztH — 270toWin (@270toWin) May 25, 2026 Trending Politics reported the final Quantus runoff numbers this way: Quantus Insights’ final survey of the Texas Republican Senate runoff showed Ken Paxton leading Sen. John Cornyn by nearly ten points. The reported topline had Paxton at 52.7% and Cornyn at 43.4%. Another 3.9% of likely GOP runoff voters were still undecided before the May 26 election. The survey was conducted May 21 through May 23 among 1,018 likely Republican runoff voters. Quantus used mobile-cell SMS outreach and a modeled Republican runoff electorate. The effective sample size was 936 voters. The weighted margin of error was listed at about plus or minus 3.5 percentage points. The poll marks a sharp turn from March, when Cornyn finished barely ahead of Paxton and forced the runoff. Paxton’s lead was reported across men, women, rural voters, suburban voters, voters without four-year college degrees, and most major media markets. Cornyn’s strongest pockets were urban voters and highly educated Republicans, but the memo said that was not enough to erase Paxton’s broader coalition. Quantus Insights framed its own survey release around Paxton holding the edge: Quantus titled the release as a survey showing Paxton holding the edge on the eve of the Texas GOP runoff. The firm’s page described President Trump’s endorsement as widely known among likely Republican runoff voters. It also said Paxton’s advantage rested on broader runoff alignment, not only on late endorsement movement. That distinction matters because most voters in the poll said the endorsement did not change their vote. Among voters who did say the endorsement moved them, the movement favored Paxton. Quantus describes its work as polling, election forecasting, economic analysis, and advanced modeling. The firm says it focuses on political and economic intelligence for elections and public policy. The survey was released just before Election Day, so it should be read as a final snapshot of the runoff electorate. It is not a declared result, but it gives Paxton a strong closing position if the modeled electorate matches Tuesday’s turnout. The Texas Tribune laid out the President Trump endorsement backdrop: President Trump endorsed Ken Paxton in the Republican runoff on May 19. The endorsement landed during early voting and gave Paxton a major boost against Sen. John Cornyn. The Texas Tribune reported Cornyn finished first in the March primary with 42% to Paxton’s 40.5%. That narrow result forced the head-to-head runoff between the longtime senator and the Texas attorney general. President Trump praised Paxton as a loyal America First fighter and criticized Cornyn for being late to support his 2024 campaign. Paxton said he was honored by the endorsement. He also said he looked forward to championing President Trump’s America First agenda in the Senate. The endorsement was a serious blow to Cornyn’s allies, including establishment Republicans who had urged the White House to support the incumbent. Rep. Wesley Hunt, who finished third in March, endorsed Paxton shortly after President Trump did. This is a Guest Post from our friends over at WLTReport. View the original article here.