3:55FILE – This photo combination shows Sen. Bill Cassidy, R-La., left, in Washington, Sept. 17, 2025 and Julia Letlow in Baton Rouge, La., Jan. 21, 2021. Jose Luis Magana Brett Duke/AP
U.S. Rep. Julia Letlow, a Republican from Louisiana who had been encouraged by President Donald Trump to launch a primary challenge against incumbent Sen. Bill Cassidy, announced on Tuesday that she is indeed challenging the two-term senator — setting up a new potentially contentious Republican primary and another test of the power of Trump's endorsement.
Letlow, in a video posted Tuesday, framed herself as a staunch ally of Trump while throwing in an implied dig at Cassidy, who she did not name.
"I have fought alongside President Trump to put America first … A state as conservative as ours? We shouldn't have to wonder how our Senator will vote when the pressure's on," Letlow said in the video. "Louisiana deserves conservative champions, leaders who will not flinch."
FILE – Julia Letlow speaks to reporters in Baton Rouge, La., Jan. 21, 2021, after signing up to run for the 5th District seat.Brett Duke/AP
Trump has long had a tenuous relationship with Cassidy, who was one of seven Republicans who voted to convict Trump following the Jan. 6 attack on the U.S. Capitol.
Cassidy, a physician and chair of the Senate Committee on Health, Education, Labor and Pensions, has also broken with the White House over health policy. He voted to advance and later to confirm Health Secretary Robert F. Kennedy, Jr. despite misgivings over Kennedy's views on vaccines, and has since spoken out against changes in vaccine policy and schedules.
Trump had weighed in on the Louisiana GOP Senate primary race late Saturday. In a post on his social media platform, Trump said that should Letlow enter what's sure to be a competitive primary race, she would get his "complete and total endorsement."
President Donald Trump speaks to the media during a press briefing in the James S. Brady Press Briefing Room of the White House, January 20, 2026, in Washington.Jim Lo Scalzo/EPA/Shutterstock
"Should she decide to enter this Race, Julia Letlow has my Complete and Total Endorsement. RUN, JULIA, RUN!!!" Trump wrote.
Cassidy sounded a defiant note on Tuesday in a press call hosted by his reelection campaign just hours after Letlow launched her campaign.
Cassidy said he welcomes more competition and pointed to his record in Congress.
"I'm a conservative who wakes up every morning thinking about, how do I make my state and my country a better place," he said.
Asked by ABC News if he feels Trump's endorsement of Letlow will be a challenge for him on the campaign trail, and if he is concerned about crossing against Trump's endorsement, Cassidy downplayed the impact of any endorsements.
U.S. Chairman of Senate Health, Education, Labor, and Pensions Committee and Senator Bill Cassidy (R-LA) attends a Committee hearing to examine safety concerns surrounding abortion medication, on Capitol Hill in Washington, D.C., U.S., January 14, 2026.Nathan Howard/Reuters
"The crux of the campaign will not be about endorsements. The crux of the campaign is, how do you make Louisiana and the United States a better place," Cassidy said.
He said as well that he did not know what Trump's motivation was in endorsing Letlow.
Democrats expressed glee at the prospect of a messy GOP primary — with a spokesperson for the Democratic Senatorial Campaign Committee claiming in a statement, "Republicans' Senate headaches just got even worse as they face another nasty primary with a Trump-endorsed candidate against a sitting Senator."
But Democrats have not yet fielded any major or well-known candidate. The Cook Political Report rates the seat as solidly Republican.
ABC News' Isabella Murray contributed to this report.
Sourse: abcnews.go.com