In a test of Donald Trump's sheer political strength, Louisiana Republicans have narrowed their candidates to two.

Congresswoman Julia Letlow and Louisiana Treasurer John Fleming are projected to advance ahead of incumbent Senator Bill Cassidy, in a major victory for the president's mission to ouster his harshest critics.

The runoff is set for June 27. 

The seeds of Saturday's Louisiana Senate primary were planted on February 13, 2021, when Senator Cassidy became one of just seven Republican senators to vote to convict Donald Trump following the Jan. 6th attack on the US Capitol.

The vote marked Cassidy persona non grata with the MAGA base almost immediately. It set in motion a years-long effort to replace him that only strengthened after Trump recaptured the White House in 2024.

Trump waited but made his move in January to endorse Congresswoman Julia Letlow, all but placing a target on Cassidy's back heading into the primary.

Fleming, a former member of Congress who served in the House of Representatives from 2009 to 2017, also came under fire in the primary election, for overlapping his time as State Treasurer with employment at a Washington, DC lobbying firm. 

Cassidy's vulnerability isn't just about January 6th. 

Despite Trump carrying Louisiana by more than 60 percent in each of the last three presidential elections, the incumbent's voting record has drifted well outside MAGA orthodoxy. 

Most notably, Cassidy was one of 15 Republican senators who sided with Democrats to pass the Bipartisan Safer Communities Act - one of the most significant gun control measures in decades and one of the defining legislative wins of the Biden presidency.

An Emerson College poll released April 30th placed Cassidy last among the three candidates. 

Asked by The Daily Mail about the results earlier in May, the senator was defiant: 'I do plan to win. So if there's a runoff, I'll be in the runoff, and we'll focus there.'

Letlow's path to this moment is rare. First elected to Congress in a 2021 special election to fill the seat of her late husband, Luke Letlow, who died of COVID-19 before he could even be sworn in, Letlow was launched into a Senate race by the sheer force of the President. 

She also is embarking in a new chapter in her personal life, having gotten engaged to Kevin Ainsworth, a Louisiana-based lobbyist, at a White House holiday party last November.

But Letlow's candidacy has not been without turbulence. 

Videos surfaced during the primary showing her advocating for diversity, equity, and inclusion policies during her interview for the presidency of the University of Louisiana Monroe, a political liability in a Republican primary increasingly defined by opposition to DEI. 

Letlow has sought to counter that narrative with her congressional record, including as a lead sponsor of the Parents Bill of Rights, which would expand parental access to classroom materials and require disclosure on transgender student policies. 

The bill passed the House but stalled in the Senate.

The third major figure in the race is John Fleming, Louisiana's State Treasurer and a former congressman who served in the House from 2009 to 2017. 

Fleming led the Emerson poll and carries a notable piece of political history: he was Speaker Mike Johnson's predecessor in his congressional seat, and the first person to endorse Johnson for the position.

That relationship has put Johnson in a delicate spot. 

Asked by NBC News on Wednesday whom he planned to vote for, Johnson said he had not yet made up his mind - describing Letlow as 'like a sister' while also noting he had worked well with Cassidy, and acknowledging Fleming as his political forefather.

Fleming's campaign has faced its own headwinds, however. He came under fire for overlapping his role as State Treasurer with employment at a Washington lobbying firm.

Saturday's primary will narrow the field to two, setting up a June 27th runoff. For Trump, the race is a test of his endorsement power in a state he dominates electorally - and a chance to complete what his allies describe as a political accountability project targeting Republicans who broke with him after January 6th. 

His political operation is simultaneously hoping to oust Representative Thomas Massie in Kentucky this week, signaling that the effort extends well beyond Louisiana.

Trump's retribution run is only getting started. Later this week, he and his political operation hope to defeat Representative Thomas Massie in Kentucky on Tuesday.