Cassidy primary defeat is a 'loss for the country,' Romney says

"The Senate to now lose an exceptionally brilliant and creative mind, an MD who chairs healthcare, and a person of character," Romney wrote Sunday in a post on X. "Bill Cassidy's departure is a loss for the country."

Trump-backed Rep. Julia Letlow and Louisiana Treasurer John Fleming both topped Cassidy in Saturday's GOP primary. They will advance to next month's runoff for the Republican nomination, while Cassidy becomes the first elected Republican senator to lose renomination since Sen. Richard Lugar of Indiana in 2012.

After Cassidy was defeated, Trump took to social media to revel in the senator's ouster.

"His disloyalty to the man who got him elected is now a part of a legend, and it's nice to see that his political career is OVER!" Trump wrote in a post on Truth Social.

"Unless you're your god's perfect idiot, the result was predictable," Kennedy said. "I mean, ground control to Major Tom. The polls have shown for well over a year that Sen. Cassidy was in trouble."

Kennedy said Trump's endorsement of Letlow "was sort of the icing on the cake."

"Bill knew that, but he decided to run anyway," Kennedy added. "I respect that. I thank him for his service."

"There's no room in this party to destroy his agenda or to destroy him and his family as a Republican," Graham said. "If you align with Democrats to stop his agenda like Massie does, you're going to lose. If you align with Democrats to drive him out of office like Cassidy did, you're going to lose."

Cassidy said in his concession speech to his supporters that "when you participate in democracy, sometimes it doesn't turn out the way you want it to."

"But you don't pout, you don't whine. You don't claim the election was stolen…. You don't manufacture some excuse," Cassidy said in an apparent jab at Trump. "You thank the voters for the privilege of representing the state or the country for as long as you've had that privilege. And that's what I'm doing right now."

Fox News Digital's Paul Steinhauser and CJ Womack contributed to this report.