In a significant political upset, a candidate endorsed by former President Donald Trump defeated incumbent Senator Bill Cassidy in Louisiana's Republican Senate primary on May 18, 2026. The result marks a major victory for Trump-aligned forces and a defeat for a senator who had voted to convict Trump in his second impeachment trial.
Cassidy, a two-term senator and physician, had drawn Trump's ire after voting to convict Trump on charges of incitement of insurrection following the January 6, 2021, Capitol riot. Trump subsequently endorsed a primary challenger, who campaigned heavily on loyalty to the former president and opposition to what he called the 'establishment' in Washington.
The Associated Press called the race shortly after polls closed, with the challenger leading by a double-digit margin. Cassidy conceded defeat, thanking his supporters and vowing to serve out the remainder of his term, which ends in January 2027.
The outcome is seen as a bellwether for the 2026 midterm elections, testing the enduring influence of Trump's endorsement within the Republican Party. Several other incumbents who crossed Trump face similar primary challenges in the coming months.
