Sen. Darline Graham and Congressman Ralph Norman are making their final push to win over South Carolina voters ahead of Election Day on Tuesday.
The winner will clinch the Republican nomination in the state's Senate race this fall.
Graham has the president on her side while Norman has two prominent former governors in his corner.
Channel 9 asked an expert who has the advantage.
"Since Trump's been in office, his endorsement has meant a lot, but this cycle, he's had some losses, as well," said Scott Huffmon, a political scientist at Winthrop University in Rock Hill.
Tuesday night we'll learn if President Donald Trump's endorsement can seal the deal for Sen. Darline Graham.
The political newcomer, and sister of late Sen. Lindsey Graham, Sen. Darline Graham, has a lot of heavy hitters in her corner, including South Carolina Sen. Tim Scott and U.S. Rep. Russell Fry, who finished third in the first round of voting.
"On Darline Graham's side, most of hers are traditional establishment Republican endorsements from current leaders. Ralph Norman is running as a disruptor. The people have been disruptors in the past," Huffmon said.
Huffmon is talking about people, including former Gov. Mark Sanford and former Gov. Nikki Haley, both of whom have come out swinging for Norman.
"Mark Sanford even lost his seat speaking against Trump," Huffmon told Channel 9. "Nikki Haley ran against Trump. Jim DeMint altered the Heritage Foundation by pushing it in a more conservative way."
Those endorsements aren't the only thing that could play a role. Last week's debate between Sen. Darline Graham and Norman could as well.
"The reason the debate matters is it's what people use to justify the decision they already made," Huffmon said. "People who, like Ralph, are going to latch onto her gaffe about foreign policy. Other than that, she actually performed well by staying on message, but that has been washed away by remembering that gaffe."
Regardless of whom they support, success will come down to turnout on Election Day.
"I wouldn't bet on a blowout or neck-and-neck because there are avenues for each, and there's no way to tell who will get out of bed and go vote," Huffmon said.
Graham enters the runoff after finishing first two weeks ago, with about 33% of the vote to Norman's 25%.
