WASHINGTON - Polls began to close in Texas, where Republican voters are choosing their nominee for U.S. Senate on Tuesday in a race that could help decide control of the chamber and may become one of the most expensive in U.S. history.

John Cornyn, a 74-year-old four-term senator backed by Republican leadership, is locked in the fight of his political life against Ken Paxton, a 63-year-old, scandal-plagued state attorney general who won President Donald Trump's endorsement last week.

Texas spans both Central and Mountain time zones, and anyone in line when polls close at 7 p.m. local time will, by law, be allowed to vote.

Paxton has led Cornyn in most public opinion polls, putting him on a collision course to face the Democratic nominee - 37-year-old state Representative James Talarico, a Presbyterian seminarian and leading fundraiser whose campaign has appealed to independent and moderate voters.

Senate Republicans' campaign arm warned in an internal memo last year that a Paxton nomination "would hand Democrats an opening to flip Texas and cause Republicans to divert hundreds of millions of dollars that would otherwise be spent winning key battlegrounds."

Cornyn reiterated that point in a Fox News interview on Tuesday, warning, "Ken Paxton will be on defense the whole time between now and November" if he wins the runoff.

Republicans hold a 53-47 majority in the Senate over Democrats, who would need to net four seats in November's election to take control of the chamber. Democrats are on defense in two states Trump won in 2024 - Georgia and Michigan - but could win the chamber by holding those two seats and flipping North Carolina, Maine, Ohio and Alaska.

A competitive race in Texas, where no Democrat has won statewide since 1994, would expand the party's path to a majority and potentially force Republicans to redirect investments from more competitive battlegrounds to protect their nominee in a state that Trump carried by nearly 14 percentage points in 2024.

In backing Paxton a week before the runoff, Trump chose loyalty over electability as he continues to flex his iron grip over Republican voters. This month, Trump's endorsement of Republican primary challengers ousted incumbents including Louisiana Senator Bill Cassidy and Kentucky Representative Thomas Massie.

"Donald Trump just endorsed a man who was impeached by his own party, indicted for felony fraud, reported to the FBI by his own staff, ordered to pay $6.6 million to the whistleblowers he tried to destroy, and whose wife is divorcing him on biblical grounds," said Lauren French, a spokesperson for Senate Majority PAC, a Democratic super PAC. Paxton has denied any wrongdoing.

LOYALTY TRUMPS ELECTABILITY

The runoff winner will face Talarico, who got a three-month head start on his general election campaign after defeating U.S. Representative Jasmine Crockett on March 3.

Talarico's initial lead in the opinion polls has evaporated, with the most recent survey showing the race in a dead heat regardless of whether he is competing against Cornyn or Paxton, with 8% of likely voters undecided.

In a three-way primary in March, Cornyn had a slim lead over Paxton but failed to cross the 50% threshold to avoid a runoff.

Political experts say Tea Party and MAGA voters are the Republicans most likely to turn out in primaries and runoffs, an electorate that favors Paxton.

Trump contrasted Paxton's "extreme" loyalty with Cornyn's wavering support. But Cornyn said he was putting his trust in Republican voters, who will "decide if they want a strong nominee to help our GOP candidates down ballot and defeat Talarico in November, or a weak nominee who jeopardizes everything we care about."

Cornyn's campaign has attacked Paxton's character from the beginning. The onslaught of attacks on "Crooked Ken" includes a dating game that allows users to swipe on Paxton's alleged mistresses.

Paxton challenged Cornyn to stop the negative ads "for the good of our party."

"We have already changed our TV ad traffic ... to ensure our campaign ends on a positive note (so) that we can focus on beating the leftist lunatic in the fall," Paxton wrote on X last week.

HOUSE RUNOFFS IN SEVERAL DISTRICTS

Voters across the state will also choose their nominees in more than a dozen congressional districts. Both parties' nominees will be chosen in the San Antonio-area 35th district, an open seat Democrats are hoping to flip.

Republicans will choose between state Representative John Lujan and U.S. Air Force veteran Carlos De La Cruz.

Democrats' preferred candidate is Johnny Garcia, a public information officer for Bexar County Sheriff Javier Salazar.

Democrats have accused Republicans of meddling in their primary through a Republican-aligned political committee called Lead Left PAC that has spent funds on boosting Garcia's opponent, Maureen Galindo, a fringe candidate who has been widely condemned for antisemitic comments.

(Reporting by Nolan D. McCaskill. Editing by Michael Learmonth, Rosalba O'Brien and Cynthia Osterman)

Copyright Reuters or USA Today Network via Reuters Connect.

This story was originally published May 26, 2026 at 7:59 PM.

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