In a stunning upset that underscores the continuing influence of former President Donald Trump within the Republican Party, Senator Bill Cassidy (R-La.) lost his bid for re-election in the GOP primary this Saturday. Cassidy, a two-term senator and the current chair of the Senate Health, Education, Labor, and Pensions Committee, placed third behind Trump-endorsed Representative Julia Letlow and state Treasurer John Fleming.

This election marks the first time since 2012 that an incumbent senator from either party has been ousted in a primary, signaling a significant shift within the GOP. Both Letlow and Fleming capitalized on dissatisfaction among MAGA supporters with Cassidy’s 2021 impeachment vote against Trump and his criticism of Trump’s controversial nominee for Health and Human Services secretary, Robert F. Kennedy Jr.

The primary result is a significant victory for Trump, who has been vocal in his criticisms of Cassidy, especially after the senator’s impeachment vote related to the events of January 6. This success follows closely on the heels of Trump's previous victories in Indiana, where he managed to replace several GOP state senators over disagreements concerning redistricting.

Letlow, who represents northern Louisiana and is serving her third term, entered the race bolstered by Trump’s endorsement and significant support from Governor Jeff Landry. The Make America Healthy Again PAC also threw its support behind Letlow, investing $1 million in her campaign, enhancing her visibility and outreach.

John Fleming, leveraging his background as a former congressman and White House aide under Trump, garnered substantial grassroots support. His late surge in the polls made the primary race highly competitive and sets the stage for a closely contested runoff.

As the dust settles, Letlow and Fleming are preparing for a runoff election scheduled for late June. Early polling suggests a tight race, though Letlow held a noticeable edge in the initial round. This runoff extends an already costly and fiercely fought battle for the GOP nomination in one of the nation's most steadfastly Republican states.

CLARIFICATION: This article has been revised to clarify that it was 2012 when the last previously elected senator lost a primary, not the last senator to lose a primary.