WASHINGTON (AP) — Republican senators will gather behind closed doors Wednesday to decide who will replace longtime Senate leader Mitch McConnell and lead their new majority next year — a decision that could shape the future of the Senate, and the party, as Donald Trump reclaims the presidency.

South Dakota Sen. John Thune, Texas Sen. John Cornyn and Florida Sen. Rick Scott have been scrambling to win the most votes in the secret ballot election, promising a new direction in the Senate even as they furiously compete for Trump's favor. It will be the first test of Trump's relationship with Congress after he won the election decisively and claimed a mandate for his agenda.

It's uncertain who will win.

Thune and Cornyn have campaigned mostly within the Senate, working senators individually and privately and raising millions of dollars for Senate GOP candidates. Both quickly mobilized in March after McConnell announced he would step aside from leadership.

Scott has run an insurgent campaign outside of the Senate, campaigning publicly as the candidate closest to Trump and winning endorsements from people who are close to the former and future president. Scott received an outpouring of support on X over the weekend as Trump allies, including Elon Musk, pushed his bid.

Who senators choose, and whether Trump ultimately endorses a candidate in the final hours, could set the tone for Trump's attempts to assert control over the legislative branch in his second presidency. His relationship with McConnell was strained in his first term, and Trump was often frustrated that lawmakers would not fully bend to his will.

Both Cornyn and Thune have drawn closer to Trump in recent months after criticizing him as he tried to overturn his election defeat in 2020. But the two longtime senators are both viewed by their colleagues as institutionalists more in the mold of McConnell, while Scott has worked to gather support outside of the Senate, and within Trump's inner circle, to pressure an overhaul within.

"We got a mandate a week ago that people want change," said Republican Sen. Tommy Tuberville of Alabama, who is supporting Scott, as he walked into a forum for the candidates on Tuesday night. "They want President Trump to have more leeway than he had last time. He was kind of tied down a little bit."

Tuberville said that whoever is chosen, he wants to make sure Trump "feels good about it."

No matter who wins, all three senators have shown they will defer to the incoming president as the leader of the party, and that they are willing to cede some of the Senate's power to do so.

When Trump posted on X Sunday that the new leader "must agree" to allow him to appoint Cabinet members and others when the Senate is on recess, avoiding confirmation votes, all three quickly signaled they were open to the idea.

To select the new leader, Senate Republicans will meet privately in a ceremonial space in the Capitol for several hours to hear the candidates make their case. Few aides are allowed in. The contenders will each be introduced and nominated by two other senators, and then they make a speech of their own. Ballots are cast secretly. If no one wins a majority on the first ballot, they proceed to a second round, and so on, until someone wins a majority of the vote.

The clubby contest is a stark contrast from the House, where lawmakers publicly announce their votes for speaker in an election on the House floor.

And aside from Scott's challenge to McConnell two years ago, in which he won 10 votes, it is the first competitive election for Republican leader in three decades. McConnell, who has been a force for the party but has repeatedly feuded with Trump, was uncontested when he first became party leader in 2007.

Unlike most previous contests, there is no clear front-runner going into the election. Because senators are casting secret ballots, the majority won't say who they are voting for. And some may never tell.

"It's a secret ballot and it's a secret ballot for a reason," said South Dakota Sen. Mike Rounds, who said early on he would support his home state colleague Thune. "Each member chooses the leader that they think they can work with the best over this two year period of time."

Rounds said that he prefers the way that Thune and Cornyn have "handled it one-on-one with everybody," but that he had talked to Scott as well. "We've got three qualified individuals," he said.

One thing all candidates agree on is change from McConnell, who called most of the shots as leader — a top demand from the far-right faction of the caucus who disagreed with McConnell on aid to Ukraine and increasingly turned on him as he feuded with Trump.

Thune, Scott and Cornyn said they would like to see more opportunity for individual senators to bring bills to the floor and offer amendments, and they have pledged to be better communicators within the conference than the often-reserved McConnell. At the forum on Tuesday evening, the three agreed on many of the issues discussed, according to senators leaving the meeting.

Thune, McConnell's current No. 2, has been seen by colleagues as an incumbent of sorts, having taken over for several weeks last year when McConnell was absent due to medical reasons. He is well-liked among his fellow senators, and was seen for some time as the front-runner in the race. But Cornyn, who served as McConnell's No. 2 before Thune, is also well-liked and has also won some commitments from colleagues.

Thune and Cornyn are similar on policy, voting generally in step with the conference but working with Democrats at times. Cornyn is a longtime member of the Senate Judiciary Committee who took a leading role on bipartisan gun legislation two years ago. Thune worked across the aisle as a former chairman of the Senate Commerce, Science and Transportation Committee.

The two differ on whether the leader should be term limited — a key demand from some in the conservative wing. Cornyn has pushed for limits, while Thune has not.

Scott, the former governor of Florida, was elected in 2018 and quickly positioned himself as a foil to McConnell, running against him for leader in 2022 and aligning with Utah Sen. Mike Lee and others who have been highly critical of the current leadership. As Thune and Cornyn wooed their colleagues all year, Scott spent most of the year tied up in his own reelection race. He handily defeated Democrat Debbie Mucarsel-Powell by more than 10 points.

Scott has campaigned on his business experience. He said Tuesday night that the pitch boils down to that "I support Donald Trump's agenda. He's got a mandate."

Also voting in the election on Wednesday are the senators-elect who handed Republicans the majority next year, even though they aren't yet sworn in. Republican Bernie Moreno, who beat Democratic Sen. Sherrod Brown, attended the forum on Tuesday night and said afterward that there was "incredible energy" in the room.

Still, he said that he hasn't decided who he will vote for. "We've got three great candidates who should get us to where we are going," he said.