A Trump-backed challenger has defeated a two-term Republican senator who voted to convict the president at his 2021 impeachment trial.

Congresswoman Julia Letlow will advance to a runoff next month, ousting incumbent Bill Cassidy, who President Donald Trump branded a disloyal disaster ahead of Louisiana's high-stakes contest on Saturday.

State treasurer John Fleming, another Trump-aligned candidate, also advanced to the Republican runoff for Louisiana's Senate seat.

The top two candidates, Letlow and Fleming, will face off again in late June as neither won a simple majority. The candidate who wins the runoff will then run against a Democratic candidate in the general election.

Cassidy, 68, was one of seven Senate Republicans who voted to convict Trump when the president was impeached after the January 6 attack on the Capitol in 2021. Trump was acquitted after the Senate voted 57-43, short of the two-thirds majority required.

Of the seven Republicans who voted to convict him, only three still serve in the Senate: Lisa Murkowski of Alaska, Susan Collins of Maine, and Bill Cassidy.

During his re-election campaign, the Louisiana senator sought to repair his strained relationship with Trump.

I don't really think President Trump likes me that much, but we work really well together, Cassidy told reporters last week, pointing to several bills he sponsored that were later signed into law by the president.

But Trump had made it clear he wanted Cassidy gone, and in January encouraged Letlow, 45, to challenge the senator.

In her victory speech, Letlow thanked Trump, stating, I want to say thank you to a very special man - the best president this country has ever had, President Donald Trump.

In his election night remarks, Cassidy did not mention Trump by name, but alluded to the president and his false claims that the 2020 election he lost had been stolen.

When you participate in democracy, sometimes it doesn't turn out the way you want it to, Cassidy told supporters in Baton Rouge. But you don't pout. You don't whine. You don't claim that an election was stolen from you.

He emphasized that American leaders should focus on the wellbeing of the general public rather than loyalty to any single individual.

Trump cheered the results on Truth Social, writing, it's nice to see that his political career is OVER! and remarked, That's what you get by voting to Impeach an innocent man.

With the contest now headed to a runoff, it remains unclear whether Trump will stay actively engaged in the race.

Letlow, who became the first Republican woman elected to represent Louisiana in Congress in 2021, won about 45% of the vote in the primary.

Fleming, her rival in the June primary runoff, is a former representative for Louisiana in Congress and worked in the first Trump administration. He narrowly beat Cassidy with around 28% of the vote, while Cassidy received 25%.

Fleming stated, Yesterday, the people of Louisiana proved that a grassroots conservative can still compete, and win, even when the political establishment and outside dark money groups spend millions of dollars trying to destroy him.