Sen. Bill Cassidy, who voted to convict President Donald Trump on impeachment charges in 2021, has lost his Republican primary in Louisiana, as two challengers aligned with Trump advanced to a runoff.

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Rep. Julia Letlow, who had Trump’s endorsement in the race, will face state Treasurer John Fleming in a June 27 primary runoff, NBC News projects.

Cassidy’s loss further cements Trump’s grip on the GOP, as the president looks to exact revenge against Republicans who have crossed him in the past. And it also means yet another Republican who voted to convict Trump during his 2021 impeachment will not be returning to Congress next year.

Letlow was leading the primary field, winning 45% of the vote to Fleming’s 28% and Cassidy’s 25%, with 93% of the expected vote in. Since Letlow fell short of winning a majority of the primary vote, the race heads to a runoff.

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No elected Republican senator has lost a primary since 2012. But Cassidy had been lowering expectations for his performance in the primary, recently telling reporters that the race was “Letlow’s to lose.” But he also expressed confidence that he would advance to the runoff.

The two-term senator had a financial advantage in the race, with his campaign and an allied group accounting for a majority of the $36 million that’s been spent on ads, according to AdImpact.

Cassidy has been dogged by some of his clashes with Trump, including his impeachment vote. He acknowledged in an interview last month that his impeachment vote “might be” a liability in the primary, but he stressed that he has continued to support the president’s policies.

“I tell people, ‘Hey, you’re married? Did ever your spouse do something that you didn’t really like?’ And you work through it,” Cassidy said. “I’m focused on the now and the future. If you want somebody delivering for our state, to make Louisiana a place where people move to set down roots, raise their children and grandchildren, I’m your guy.”

But Cassidy’s impeachment vote did not sit well with some Louisiana voters, like Elias Jacob FaKouri.

“He tried to impeach Trump, and Trump helped him get elected. That’s pretty low,” FaKouri, a Fleming supporter, said at a polling place in Baton Rouge.

“It is time for him to go,” Fakori later added.

Cassidy, a physician, was also in the spotlight during Health and Human Services Secretary Robert F. Kennedy Jr.’s confirmation, given their disagreements over vaccines. Cassidy voted to confirm Kennedy to the post and has since walked a delicate tightrope between criticizing HHS over issues like vaccines while trying not to antagonize Trump.

Cassidy’s backers were not turned off by his clashes with Trump, instead praising his independent streak.

“It shows that he’s less influenced by a party, which I like,” Donny Gutierrez said at the Baton Rouge polling place, later adding, “I think we need a lot more of that.”

As Cassidy has made his own case ahead of the primary, he and his allies have also attacked Letlow over her stock trades and her past support for diversity, equity and inclusion efforts when she was working at the University of Louisiana, dubbing her “Liberal Letlow.”

Letlow has dismissed those attacks by saying a third party has managed her stock trades, and that she has shifted her stance on DEI initiatives.

“Cassidy is lying about me because he can’t defend his own record,” Letlow told NBC News last month.

Letlow, meanwhile, has been touting her endorsement from Trump on the airwaves, with a boost from an allied outside group. Letlow also has the backing of GOP Gov. Jeff Landry.

She has attacked Cassidy and Fleming as “never Trumpers” and said when she launched her Senate run, “A state as conservative as ours, we shouldn’t have to wonder how our senator will vote when the pressure’s on.”

Letlow told NBC News last month that the president’s endorsement has been “a huge source of energy for our campaign, because Louisiana Republicans trust President Trump.”

“When the president tells you need to step up, and when the voters in Louisiana are really encouraging, saying, we want an alternative, we want another choice, would you consider doing this? Would you pray about it? And you know, when I had that piece about it, I decided to go all in,” Letlow said.

Letlow was first elected to the House in 2021, succeeding her husband who died of Covid before he was sworn into office.

Fleming has cast himself as a Trump ally even though he doesn’t have the president’s backing, launching an ad that he is the “true conservative” in the race who was “MAGA before MAGA was cool.”

Fleming was elected as state treasurer in 2023 after serving in the first Trump administration. He served in Congress from 2009 to 2017 and was a founding member of the hard-right House Freedom Caucus, leaving the House to make an unsuccessful run for Senate in 2016.

The former congressman has largely self-funded his Senate run, loaning his campaign $10.6 million. He launched his campaign back in December 2024, long before Letlow jumped in the race, criticizing Cassidy for his 2021 impeachment vote.

Fleming did say he faced some pressure to end his campaign and clear a path for Letlow to take on Cassidy, telling NBC News that someone “around” the Trump administration offered him a job to get him out of the race. The White House did not respond to a request for comment.

As the race heads to a runoff, it’s not clear if Trump will become more engaged in the race.

A Trump political adviser recently told NBC News that Trump and his orbit are more focused on defeating Kentucky GOP Rep. Thomas Massie in a May 19 primary, saying of the president, “There is no way he views Cassidy and Massie the same.”

The president had not traveled to Louisiana to boost Letlow’s campaign ahead of Saturday’s primary, though he appeared in a TV ad for Letlow and recently posted on Truth Social blaming Cassidy for tanking his surgeon general nominee. Trump also encouraged voters to reject Cassidy on Saturday morning, calling the senator a “disloyal disaster.”

It is not yet clear who will win the Democratic nomination, or if that primary will also head to a runoff. But Republicans are expected to be in a strong position to hold the seat in November.

Republicans running for federal office have dominated recent elections in the Pelican State, which Trump won by 22 points in 2024.