Washington — CBS News projects Rep. Julia Letlow and Louisiana state Treasurer John Fleming advanced to a runoff in Saturday's Senate Republican primary, knocking out incumbent GOP Sen. Bill Cassidy. 

Cassidy, 68, was one of seven Senate Republicans who voted to convict President Trump in his impeachment trial after the Jan. 6 attack on the Capitol in 2021. And although he's emphasized his cooperation with the administration in recent years, the president endorsed Letlow in January, encouraging her to challenge Cassidy for the seat. 

Letlow, 45, became the first Republican woman elected to represent Louisiana in Congress in 2021 after winning a special election for Louisiana's 5th Congressional District following the death of her husband, who died in 2020 from complications related to COVID-19 before he could be sworn into office. She's hammered Cassidy as disloyal to the GOP, claiming Louisiana "shouldn't have to wonder how our senator will vote when the pressure's on."

Letlow had touted her endorsement from Mr. Trump, while Fleming, who worked in the first Trump administration and represented Louisiana in the U.S. House, had called himself "the only conservative MAGA Republican" in the race. 

In addition to his vote to impeach Mr. Trump, Cassidy has been at odds with the administration over HHS Secretary Robert F. Kennedy Jr.'s leadership, despite delivering the key vote to advance Kennedy's nomination last year. Cassidy, a medical doctor, has broken with the HHS secretary on multiple occasions, including slamming a change to the hepatitis B vaccine schedule for infants and calling for the postponement of key vaccine advisory panel meetings.

While Letlow accused Cassidy of not being sufficiently conservative, Cassidy claimed the same about his Trump-backed opponent, pointing to comments she made in 2020 supporting DEI programs in education. Fleming had also accused Letlow of supporting DEI. 

The contest is the latest sign of the president's influence, despite approaching the back half of his final term. Earlier this month, Mr. Trump's gambit to push Republicans out of the state Senate in Indiana who defied his redistricting efforts were largely successful. 

Meanwhile, the Senate Republicans' campaign arm, the National Republican Senatorial Committee, had supported Cassidy, who was seeking a third term in the Senate. Senate Majority Leader John Thune told reporters Thursday that "Bill Cassidy has been a terrific senator for Louisiana."

"Tim Scott and I at the NRSC, our job is to do what we can to support incumbents," Thune said. "But obviously the voters of Louisiana are going to make that decision."

On the Democratic side, Nick Albares, a former policy advisor to Gov. John Bel Edwards, Navy veteran Gary Crockett and third-generation farmer Jamie Davis were facing off for their party's nomination. But Louisiana is a solidly red state, where Mr. Trump won 60% of the vote in 2024. And the state last elected a Democrat to the Senate in 2008, making the winner of the GOP primary likely to face a glidepath to the Senate in November's general election. 

Louisiana's Republican Gov. Jeff Landry suspended the state's House primaries in the wake of the Supreme Court decision to strike down the state's congressional map earlier this month, while other races, including the Senate primaries, were set to go on as planned.