Julia Letlow launches Trump-backed GOP primary challenge to Cassidy

Rep. Julia Letlow announced she will seek the U.S. Senate seat held by Sen. Bill Cassidy, escalating a high-stakes Republican primary that tests former President Donald Trump's influence in Louisiana GOP politics. The congresswoman made the declaration at a closed-door breakfast in Baton Rouge and shortly afterward posted a campaign video and message on social media.

Audio of the breakfast captured her saying, “It’s an honor to share with you, after the endorsement and encouragement from the president, the president of the United States, Trump, that today I will officially be announcing my candidacy for the U.S. Senate.” The announcement followed a weekend social media post from Trump that urged her to run with the words, “RUN, JULIA, RUN!!!”

Letlow framed her bid as a defense of the party’s domestic policy agenda, including a tax bill signed last summer, and positioned herself as a staunch Trump ally. In an 18-minute appearance, she did not mention Cassidy by name, instead emphasizing alignment with priorities that have become litmus tests in the post-2020 Republican Party.

Her entry places the White House-era political force behind a primary challenge to a sitting senator. The National Republican Senatorial Committee has continued to back Cassidy as the incumbent, and Senate leaders publicly showed support for him in Louisiana in recent days. Cassidy, a two-term senator who chairs the Senate Health, Education, Labor and Pensions Committee, will face his first electoral test since voting to convict former President Donald Trump on impeachment charges following the Jan. 6, 2021, attack on the U.S. Capitol.

Cassidy responded by downplaying the role of outside endorsements in the contest, saying, “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,” and questioning the motive behind the presidential backing.

The Republican primary is scheduled for May 16, 2026, under Louisiana’s closed primary rules for federal contests, with only Republicans and independents eligible to participate. If no candidate secures a majority, the top two finishers will advance to a runoff in June. Several Republicans have already declared challenges to Cassidy, including former U.S. Rep. and state Treasurer John Fleming, state Rep. Julie Emerson, and state Sen. Blake Miguez, signaling a potentially crowded and costly primary.

Political operatives see the contest as a barometer for Trump’s sway over GOP primaries and congressional endorsements. Governor Jeff Landry, who had identified Letlow as an attractive challenger and aligned closely with the former president, has been active in nationalizing Louisiana politics, including engagements over international issues that have drawn attention.

Democrats welcomed signs of intra-party conflict, with the Democratic Senatorial Campaign Committee saying, “Republicans' Senate headaches just got even worse as they face another nasty primary with a Trump-endorsed candidate against a sitting Senator.” Political forecasters continue to regard the seat as safely Republican, but strategists warn that a bruising primary could deplete resources and reshape the general election dynamics in a year when Senate control margins are expected to be narrow.