The storied career of Sen. John Cornyn came to a swift and decisive end at the hands of the GOP voters who once propelled him to power.

The senator was a towering figure in both national and Texas politics, known for his sober temperament, ability to cut deals and role in shaping the Senate GOP conference during the last four presidencies. Then, just about an hour after polls closed Tuesday, Cornyn lost his primary to Ken Paxton, a scandal-plagued MAGA darling who was boosted by President Donald Trump’s last-minute endorsement.

Cornyn’s defeat is rattling the establishment wing of the GOP, who viewed the brutal primary as a battle for the soul of the party. His supporters mourn his approaching absence in the Senate as another example of an institutionalist who fell victim to the rise of the populist right, what they see as the end of an era of compassionate conservatism.

“It just blows my mind that anybody could look at John Cornyn and somehow call him a secret liberal RINO,” said Josh Schroeder, mayor of Georgetown, Texas, and a Cornyn supporter. “If that guy can’t pass a conservative litmus test, who can?”

Cornyn’s loss stands to further deplete the corps of senators willing to work across the aisle on thorny policy issues, from immigration reform to gun safety — potentially contributing further to increasing polarization on Capitol Hill.

While Cornyn was not a frequent bipartisan operator in the mold of former Sens. Joe Manchin (I-W.Va.) or Rob Portman (R-Ohio), he occasionally dug in to try and find compromise. His loss comes just ten days after fellow Sen. Bill Cassidy (R-La.) lost his own primary to a Trump-backed challenger. Before that, it had been 14 years since the last elected senator lost a primary.

“He’s always been about delivering results for Texas rather than chasing headlines,” said Brian Walsh, Cornyn’s former communications director. “He respects the Senate as his institution and believes deeply in doing the work the right way, even when it’s difficult, or I would say politically inconvenient.”

His participation was often crucial as a member of the GOP leadership team and a key Republican fundraiser who operated with the tacit approval of Kentucky Sen. Mitch McConnell, who served as GOP leader for nearly all of Cornyn’s tenure.

Even though his supporters were long skeptical of his odds in the primary, Cornyn chose to go down swinging. He continued to run negative ads against Paxton throughout Texas until the last minute, harping on Paxton’s indiscretions. And he warned during an appearance on Fox News on Tuesday that the attorney general would be an “albatross” on the rest of the Republican ticket “likely to have a negative drag on the down ballot races in Texas, judges, local officials, House of Representatives, you name it.”

But those moral arguments did not sway a majority of primary voters — or Trump, who chose to endorse the attorney general and cited Cornyn’s decision to wait to endorse his third presidential run as proof he was insufficiently loyal.

Paxton’s supporters have long shrugged off his long trail of criminal and ethics investigations, impeachment by the state legislature and ongoing divorce, complete with accusations of infidelity, believing that his commitment to carrying the MAGA torch was more important than corruption allegations or a messy personal life. Paxton, for his part, has tried to focus the campaign on his qualifications for the Senate — and allegiance to Trump.

Paxton also benefitted from a strong anti-incumbency sentiment rippling throughout Texas. The GOP base was ripe for his argument that Cornyn was too enmeshed in the D.C. swamp to justify sending back to Washington even as those attacks bewildered Cornyn’s supporters, who pointed to his long record of voting for Trump’s agenda.

As majority whip during Trump’s first term, Cornyn helped shepherd the president’s signature tax bill across the finish line. In 2024, he fell just a few votes short of becoming majority leader against Sen. John Thune (R-S.D.). And few Republicans have demonstrated fundraising prowess like Cornyn, the former chair of the National Republican Senatorial Committee, who has brought in more than $400 million throughout the course of his political career.

“Senate Republicans were very eager to see their friend and colleague continue, and Cornyn is one of those guys that would’ve raised money for his fellow incumbents. That’s unlikely to continue,” said a GOP Senate strategist, granted anonymity to speak candidly.

Trump, after weeks of standing on the sidelines, swooped in at the start of early voting to back Paxton, a reward for the attorney general supporting his efforts to overturn the 2020 election. Cornyn, on the other hand, voted to certify the results.

Throughout the bitter campaign, Cornyn shifted to the right on some issues, adopting the fiery language of the MAGA base, which was seen as an effort to endear himself to Trump in a bid for his endorsement. Most prominently, he ran an ad declaring that “radical Islam is a bloodthirsty ideology.”

When Paxton cleverly declared that he would drop out of the primary if the Senate GOP killed the filibuster to pass the SAVE America Act, Trump’s priority election bill, that staved off the president’s planned endorsement of Cornyn. The Texas senator belatedly announced a reversal of his longheld support of the filibuster. And Cornyn introduced a bill two weeks ago to rename a major U.S. highway Interstate 47 to honor Trump. But it came far too late to save him.

But in a hyper-partisan environment, Cornyn’s decisions to occasionally work with Democrats doomed his standing among the rabidly conservative base in Texas.

Cornyn kept to the outskirts of high-stakes bipartisan immigration talks, such as the “Gang of Eight” that sought a comprehensive overhaul in 2013. But he later partnered with Sen. Kyrsten Sinema of Arizona in exploring a narrower, border-security-focused bill.

He also found success reaching across the aisle in 2022 on gun safety legislation in the aftermath of the Uvalde school shooting. The Bipartisan Safer Communities Act was modest relative to Democratic demands for stricter gun control. But it was still the most significant federal gun legislation in a generation — and it provoked intense backlash among hard-right voters in Texas.

“We both know that when we’re doing what’s right, it doesn’t matter what other people think,” Cornyn texted Sinema at the time.

Four years later, Paxton made the legislation a centerpiece of his campaign, accusing Cornyn of shepherding “the worst gun control bill in decades.”

Texas will now be swept up in an expensive and competitive Senate race, with Democrats amped to compete against Paxton, who they view as more vulnerable than Cornyn in a midterm environment favorable to their party. Many believe Democratic nominee and state Rep. James Talarico is their best shot in a generation at flipping a statewide seat.

Schroeder, who represents a small town in Talarico’s former district, said the Democrat is capable of pulling off a strong campaign: “He appears to be campaigning from the high road while the Democratic party is just slicing Paxton to shreds because they got a whole lot of ammunition.”

In the aftermath of the brutal primary, some Republicans fear that the state of the GOP is dire – and potentially unable to unify ahead of November with the possibility that some Cornyn supporters will sit out the race entirely or vote for Talarico. After the race was quickly called on Tuesday, Talarico posted on X: “To Senator Cornyn’s supporters: you have a place in our campaign.”

In his concession speech, Cornyn said he will support the GOP ticket: “I’ve fought the good fight, I’ve finished the race, and I’ve kept the faith.”

“I’ll have more to say later.”

Mike DeBonis and Samuel Benson contributed to this article.