SOUTHAVEN, Miss. — President Donald Trump is looking to use his influence to sway the outcome of a low-profile election in Mississippi that could tip the balance of the Senate.

As Republicans fight headwinds ahead of the Nov. 6 midterm election, Trump rallied his supporters on Tuesday behind Sen. Cindy Hyde-Smith, who was appointed to fill the seat of Republican Thad Cochran, who retired in April. She faces three candidates — Republican Chris McDaniel and Democrats Mike Espy and Tobey Bernard Bartee — in next month’s special election for the remainder of the two-year term.

“She’s always had my back,” Trump said. “She’s always had your back. And a vote for Cindy is a vote for me.”

Republican officials and the White House expect Hyde-Smith’s race to go to a runoff under the state’s election rules that force a showdown between the top two finishers if no candidate wins at least 50 percent of the vote on Election Day. With Republicans defending majorities in the House and Senate next month, officials cast Trump’s visit as an attempt to get ahead of a potentially perilous situation.

Officials said Trump is seeking to boost Hyde-Smith as close as possible to the 50 percent threshold and lend momentum for a possible runoff. Depending on how Republicans perform on Nov. 6, the eyes of the nation could fall on a Nov. 27 Mississippi runoff in what could become an expensive and high-profile race to determine control of the Senate.

“Your vote in this election will decide which party controls the United States Senate,” Trump said.

Trump’s support for Hyde-Smith is hardly without controversy — even at one of his own rallies. A vocal minority of the crowd on Tuesday backed McDaniel, a conservative state senator, and booed Hyde-Smith when Trump introduced her. They even launched into occasional chants of “We want Chris.”

Trump also attacked Espy, a former congressman and the leading Democratic contender, saying a vote for him “is a vote for the Democrat agenda.”

“This is also a referendum about me and the disgusting gridlock they’ll put this country through,” Trump added of Democrats.

Trump devoted much of the rally to criticizing scrutiny of his Supreme Court nominee, Judge Brett Kavanaugh, whose confirmation has been delayed over allegations that he engaged in sexual misconduct decades ago.