Thune, Cornyn and Scott make their case to be next Republican Senate leader

Each will argue he's best-suited to carry out Donald Trump's agenda.

Three senators are running to replace Mitch McConnell, who has served atop the Senate Republican Conference for a record-breaking 17 years. With McConnell announcing his intent to step aside earlier this year, Sen. John Thune, the current Republican whip, is running against Sen. John Cornyn, a Texas senator and former Republican whip, and Sen. Rick Scott, a Florida Republican who just won reelection to his second term.

Ahead of the vote, slated for Wednesday morning, Republicans gathered behind closed doors for over two hours Tuesday evening to hear arguments from Thune, Cornyn and Scott, as well as other senators who are running for downballot leadership positions. Any other candidate who might wish to throw their name in the running for party leadership would have been permitted to do so during the meeting.

It was described by Senators in the room as "energetic" but not a debate.

When the meeting was over and Thune exited the event, he told reporters that Tuesday night was an opportunity for the conference to hear from the candidates.

When asked specifically about the whip count, Thune remained vague.

"You never know until the voters vote," Thune said.

Cornyn kept quiet leaving the room, "I'll make my pitch to my colleagues, not to you."

Even before the Tuesday meeting, the candidates were beginning to make their closing arguments and working to assert their loyalty to Trump, whose influence could certainly sway the outcome of the race.

Cornyn wrote a letter to colleagues Tuesday, obtained by ABC News, in which he repeatedly touted his commitment to Trump's agenda and confirmation of his Cabinet selections.

"It's imperative that Republicans hit the ground running to implement President Donald Trump's agenda for the American people," Cornyn wrote in the letter, citing GOP success across the House, Senate, an White House.

Scott, meanwhile, has made appearances on cable news outlets in recent days and touted his endorsements from a number of Trump-aligned outside influencers, including Elon Musk and Robert F. Kennedy Jr. He's tried to position himself as the most Trump-aligned candidate.

And Thune, who perhaps has had the iciest relationship with Trump among the contenders, also made clear he's been in regular contact with Trump's team, and he's made public statements supporting Trump proposals, including potential changes to Senate operating procedure.

Trump has not endorsed a candidate in the leadership race, opting instead to insist that whichever candidate is selected will support his use of recess appointments, which would allow him to temporarily fill federal vacancies without Senate approval.

All three candidates have signaled their willingness to use that strategy to quickly fill out Trump's Cabinet.