Texas Attorney General Ken Paxton defeated Sen. John Cornyn (R-Texas) in the Texas Republican runoff on Tuesday, resoundingly winning 62% to Cornyn’s 37%. The contest has exposed deep fractures inside the GOP and tested President Donald Trump’s grip on the party.

Paxton, a longtime Trump ally, entered the final stretch of the race with momentum after securing Trump’s endorsement earlier this month.

Cornyn, a four-term senator and former Senate Republican whip, has fought back with a flood of television ads and support from establishment Republicans in Washington and Texas.

The increasingly personal campaign has become a proxy war between the party’s traditional conservatives and its MAGA wing. Republicans close to both camps now worry the damage could linger well beyond the runoff.

Cornyn allies have hammered Paxton over years of legal controversies and impeachment proceedings in the Texas House. Paxton’s supporters, meanwhile, have argued Cornyn represents an outdated version of the Republican Party that failed to fully embrace Trump’s political movement.

Trump added fuel to the feud over the weekend, posting on X that Cornyn was “VERY disloyal to me” while claiming Paxton “WILL NEVER LET YOU DOWN!!!”

The endorsement stunned many Republicans in Washington, where Cornyn has long been viewed as one of the party’s most reliable and influential senators. Some GOP strategists fear a Paxton victory could weaken Republicans in the general election and force the party to spend heavily to defend a seat once considered safely red.

Democrats are closely watching the fallout. Rep. James Talarico (D-Texas), the party’s nominee, has posted strong fundraising numbers and has performed competitively in early polling against both Republicans, especially Paxton.

Behind the scenes, some Republican donors are already signaling hesitation about financially backing Paxton.

“With Trump going all in on Paxton, the larger ecosystem is looking to Trump to cover any additional costs to carry Paxton across the finish line there,” the strategist said.

For Cornyn, a defeat would mark a dramatic fall for a politician once considered untouchable in Texas Republican politics. He has represented Texas in the Senate since 2002 and built deep ties to the state’s influential donor network.