Bill Cassidy is among seven Republican senators who voted to convict Trump after the January 6, 2021, Capitol attack.

US Senator Bill Cassidy has lost his Louisiana Republican primary after years of criticism from supporters of Donald Trump over his vote to convict the United States president during his 2021 impeachment trial linked to the January 6 Capitol attack that year.

Cassidy failed to secure enough support in the southern state on Saturday to advance to a run-off, finishing behind Representative Julia Letlow and State Treasurer John Fleming. The two will face each other in a second round of voting on June 27.

The result underlines Trump’s continued influence over the Republican Party as he targets politicians seen as disloyal, even as he faces growing political pressure over inflation, falling approval ratings and criticism of the US-Israeli war on Iran.

Cassidy was one of seven Republican senators who voted to convict Trump after the attack on the US Capitol by Trump supporters who sought to overturn Trump’s 2020 election loss. While several Republicans who broke with Trump chose not to seek re-election, Cassidy campaigned aggressively for a third six-year term and heavily outspent his rivals.

On the morning of the vote, Trump attacked Cassidy on social media, calling him “a disloyal disaster” and “a terrible guy”. Speaking after his defeat, Cassidy appeared to respond indirectly to Trump’s remarks. “Insults only bother me if they come from somebody of character and integrity,” he told supporters.

He added: “Our country is not about one individual. It is about the welfare of all Americans, and it is about the constitution.”

Letlow, meanwhile, embraced Trump’s backing during her victory speech. “I want to say thank you to a very special man, … the best president this country has ever had, President Donald Trump,” she said.

She later described Cassidy’s impeachment vote as evidence that he had “turned his back on Louisiana voters”. Trump celebrated Cassidy’s loss online, writing: “That’s what you get by voting to impeach an innocent man.”

The Louisiana race is the latest in a series of contests in which Trump has backed efforts to remove Republicans who opposed him. Earlier this month, several Indiana state senators were also defeated after they had rejected Trump’s redistricting plan aimed at winning more seats in the US Congress for Republicans.

Saturday’s elections also took place amid confusion after a recent US Supreme Court ruling weakening part of the Voting Rights Act related to electoral district maps.

While the Senate primary went ahead as planned, Louisiana officials postponed primary elections for the US House of Representatives to redraw district boundaries. Civil rights groups challenged the delay, arguing it violates both the US Constitution and the Louisiana Constitution.