Republican Presidential candidates will have to pledge support for the eventual nominee in order to be included on the Republican National Committee's debate stage, RNC chair Ronna McDaniel said Sunday.

McDaniel says candidates will have to sign the pledge prior to the first primary debate, which will be held in Milwaukee. Former President Trump has expressed opposition to the pledge, however, echoing his hesitancy to make the same pledge in 2016.

"We’re saying you’re not going to get on the debate stage unless you make this pledge," McDaniel said on CNN's "State of the Union" on Sunday. "Anyone getting on the Republican national committee debate stage should be able to say, 'I will support the will of the voters and the eventual nominee of our party."

"I think they're all going to sign it. I really do," McDaniel added. "I think President Trump would like to be on the debate stage."

THIS STATE WILL PLAY AN OUTSIZED ROLE IN PICKING THE 2024 GOP PRESIDENTIAL NOMINEE

Ronna McDaniel

RNC Chair Ronna McDaniel says GOP candidates will have to pledge support for the eventual nominee if they want to join the RNC debates. (Kyle Grillot/Bloomberg via Getty Images)

Former President Donald Trump

Former President Donald Trump has said he doesn't want to sign a pledge to support any Republican nominee. (Jabin Botsford/The Washington Post via Getty Images)

Trump himself indicated he wouldn't support such a pledge in an interview with conservative radio host Hugh Hewitt in January.

"It would have to depend on who the nominee was," Trump told Hewitt when asked about losing the nomination to someone else.

TRUMP'S IN - SO IS HALEY - HOW LARGE WILL THE GOP 2024 FIELD GROW?

So far, only Trump and former South Carolina Gov. Nikki Haley have formally announced their candidacy for 2024. Several others may enter the ring, however, including former Vice President Mike Pence, former Secretary of State Mike Pompeo, and Florida Gov. Ron DeSantis.

Trump himself has some staunch opponents within the Republican Party, including former Speaker Paul Ryan. Ryan pledged this weekend that he would not attend the Republican National Convention if Trump was the nominee.

Nikki Haley 2024 Charleston S.C.

Nikki Haley announced her 2024 bid for President in Charleston, SC in front of a crowd of several hundred supporters. She is the only formally-declared Republican candidate aside from Donald Trump. (Fox News)

Mike Pence

Former Vice President Mike Pence is likely to throw his hat in the ring for the 2024 Republican presidential nomination. (Tom Williams/CQ-Roll Call, Inc via Getty Images)

"If we nominate Trump again, we're going to lose. It's just that clear," Ryan told Fox 6 last week. "We lost with him in ‘18, ’20 and '22. We know this. He will cost us another election, so I'm just excited about somebody not named Trump."

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"There are great people running. I know them all. They're all pretty decent friends of mine, and so I think any one of these candidates that are thinking about getting in the race if they get in the race, would be a great candidate," he added. "I think we're going to beat Joe Biden if we don't run Donald Trump."