President Donald Trump’s endorsement will once again be on the ballot Saturday in the GOP primary runoff for Senate in Louisiana. And low voter turnout could make for an unpredictable race, potentially threatening Trump’s ability to define the terms of the contest in the Bayou State.

Trump already ousted GOP Sen. Bill Cassidy, who voted to convict Trump during his second impeachment trial, following the Jan. 6, 2021, Capitol riot. The incumbent finished in third place during the May 16 primary, winning just 25% of the vote and failing to qualify for the runoff.

Louisiana Senate primary runoff results

Instead, Trump-backed Rep. Julia Letlow finished first in that contest with 45% of the vote, followed by state Treasurer John Fleming at 28%. Since no candidate won a majority, Letlow and Fleming headed to a runoff.

Letlow is expected to have an edge in Saturday’s contest thanks in large part to Trump’s support.

Trump urged supporters to back Letlow during a tele-rally with the congresswoman Thursday evening, describing her as a “fearless champion” for the state. Letlow in turn pledged to support Trump’s “America First” agenda and framed the race as a choice between “a real conservative fighter or another career politician.”

But some Louisiana Republicans say Fleming could pull off a victory in a runoff if there is very low turnout and few but the most ardent conservatives head to the polls.

“I believe that she’s going to win,” Louisiana GOP strategist Lionel Rainey III, who is not involved in the race, said of Letlow. “But I think it’s going to be much, much closer than anybody expects and I would not be shocked if [Fleming] somehow edged this thing out. I don’t think that’s probable. I do think it is possible.”

Fleming believes he can appeal to Trump’s faithful supporters, especially as voters take a fresh look at the candidates.

“The dynamic leading up to the primary was: No matter what you said, everybody was focused and obsessed really with stopping Cassidy from being re-elected,” Fleming told NBC News. “We heard over and over, ‘Anybody but Cassidy. Anybody but Cassidy.’ And so I think for a lot of people, it really didn’t matter who got elected.”

“A lot of people just viewed Julia Letlow as the conduit, the way to stop Cassidy,” Fleming continued, later adding, “The dynamic now is completely different. People are actually looking at the candidates, and what they see is I’m far more conservative in my practice, in my votes, in everything that I do.”

A former congressman and founding member of the hard-right House Freedom Caucus, Fleming also served in the first Trump administration, including as deputy chief of staff in the final months of the term.

Fleming has cast himself as the true “MAGA conservative” in the race, knocking Letlow for her past support for diversity, equity and inclusion policies and foreign aid. Letlow told NBC News earlier this year that she reversed her position on DEI when she “saw it for what it was” and has since been “fighting against it.”

But Trump’s endorsement could make that argument against Letlow a tough sell, Louisiana GOP strategist James Hartman said.

“The fact that he endorsed her right out of the gate, again, inoculated her against any sort of claim that she’s liberal because folks tend to still perceive President Trump as being conservative,” Hartman said.

Fleming believes Trump backed Letlow at the urging of GOP Gov. Jeff Landry, who has also endorsed the congresswoman in the race. Fleming said he spoke with the president over the phone after Trump endorsed Letlow and Trump called him “fantastic.”

Trump did not mention Fleming during the Thursday tele-rally, instead heaping praise on Letlow, saying, “Perhaps most importantly, she’ll support the SAVE America Act to protect our sacred American elections,” referring to a measure he’s backing to overhaul U.S. election laws.

“I am the only candidate in this race who agrees with President Trump that the Senate should nuke the filibuster in order to pass the SAVE America Act,” Letlow later added.

Fleming said he would be open to eliminating the filibuster to pass the bill.

“I’m willing to do whatever — reconciliation, the talking filibuster, even kill the filibuster altogether — whatever is necessary. But there seems to be no consensus among Republicans first of all to pass the bill,” Fleming said. He added that his “reluctance” about nixing the filibuster stems from concerns that Democrats could easily pass their priorities through a filibuster-free Senate the next time they take control of Congress.

Letlow has also gotten a boost on the airwaves from allied super PACs, and she has support from other high-profile Louisiana Republicans, including House Majority Leader Steve Scalise and Rep. Clay Higgins.

Higgins endorsed Letlow after Fleming shared an AI-generated video featuring a deepfake of Letlow saying, “My poor husband died and I was appointed to his congressional seat,” which Higgins said was “nasty on another level.” Letlow was first elected to the House in a 2021 special election, which took place after her husband died of Covid before he was sworn into office for that term.

Fleming has said his campaign has not created AI videos but “parody ads are OK.” He has since deleted the social media post.

Whatever else has happened in the campaign, it’s Trump’s endorsement that has been the biggest boon for Letlow, and it could propel her to victory on Saturday, said Hartman, the GOP strategist.

“When he says ‘Letlow is the one to back my agenda,’ the faithful are going to fall in line,” Hartman said.