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(WASHINGTON) — Republican presidential candidates who qualify for the first primary debate will have to satisfy one final, somewhat controversial requirement, sources say: signing a pledge to back whomever the party’s eventual nominee is, including if it’s Donald Trump.

Two sources familiar with the discussion told ABC News that the pledge will only be presented to candidates for their signature after they earn their spot on the debate stage, in Milwaukee in August, rather than earlier in the process.

This order would signal that they cannot lean on the pledge as a reason not to participate.

Three GOP hopefuls who are critical of Trump — former New Jersey Gov. Chris Christie, former Arkansas Gov. Asa Hutchinson and former Texas Rep. Will Hurd — have expressed concerns about the pledge.

Trump himself has not committed to backing another candidate should he lose the primary.

A spokesperson for the Republican National Committee, asked for comment, referred ABC News to what RNC Chair Ronna McDaniel said on Fox News last week: that the pledge was about backing voters’ views.

“Anybody who wants to seek the nomination of our party should pledge to support the voters,” McDaniel said then. “If you go through this process and you take time on the debate stage and you’re going to be there, the No. 1 pledge should be: Beat [Joe] Biden.”

All candidates have up until 48 hours prior to the Aug. 23 debate to prove to the RNC that they’ve hit at least 1% in three national polls or in a mix of national and early state polls recognized by the committee plus accrued 40,000 individual donors to their campaigns from at least 200 unique donors per state in 20 or more states.

Hutchinson, who is polling at 1.1% according to an average from FiveThirtyEight, has publicly objected to both the loyalty pledge requirement and donor threshold, which he said was too limiting.

His campaign pressed RNC officials to reconsider the pledge after Trump was federally charged earlier this month, now facing two criminal prosecutions. (Trump has pleaded not guilty in both.)

During a call between RNC leaders and a staff member of the Hutchinson campaign on June 15, party officials insisted there would not be any changes to their debate guidelines.

“Individuals who are seeking the Republican nomination for President are being asked to respect the decision of Republican Primary voters and support the eventual nominee they pick to beat Biden,” RNC senior adviser Richard Walters told ABC News’ Rachel Scott in a statement. “Candidates who are complaining about this to the press should seriously reconsider their priorities and whether they should even be running.”

Hutchinson’s campaign subsequently took issue with the party’s plan not to deliver the loyalty pledge to candidates until they have met donor and polling benchmarks.

“It’s been our understanding that the text of the pledge would be provided to the campaigns well in advance of whatever deadline is set by the RNC,” Hutchinson’s campaign manager, Rob Burgess, told ABC News.

Nonetheless, Burgess said, “I am confident Gov. Hutchinson will be on the debate stage in order to demonstrate what true consistent conservative leadership looks like.”

Christie has also made his displeasure with the pledge clear, calling it a “useless idea” and telling ABC News anchor George Stephanopoulos earlier this month that he would take the pledge “just as seriously as” Trump did in the 2016 election cycle — that is to say, he would disregard it as needed.

During the 2016 cycle, Texas Sen. Ted Cruz and then Ohio-Gov. John Kasich also suggested they would drop the pledge. Cruz later endorsed Trump.

A spokesperson for Christie’s campaign referred ABC News to what Christie said on CNN in regard to his thoughts on the pledge, which they said he’s also expressed directly to McDaniel and the RNC.

“In all my life, we never had to have Republican primary candidates take a pledge. You know, we were Republicans. And the idea is you support the Republicans, whether you won or whether you lost. And you didn’t have to ask somebody to sign something. It’s only the era of Donald Trump that you need somebody to sign something on a pledge. So I think it’s a bad idea,” Christie said on CNN.

“But look, I will do what I need to do to be up on that stage to try to save my party and save my country from going down the road of being led by three time loser Donald Trump.”

Hurd, upon his long shot entrance into the GOP field last week, hesitated when asked on CNN if he thought he would be able to get on the debate stage.

He also said he wouldn’t sign a candidate pledge or support Trump should Trump become the nominee. He suggested that the RNC was attempting to tip the scales of the primary by implementing debate requirements like the pledge.

“The bottom line is this: I’ve taken one pledge and that’s when I put my hand on the heart to pledge allegiance to the flag. I’ve taken one oath, asked to defend the Constitution of America. And I’ve taken one vow, to my amazing, beautiful wife,” Hurd said.

In response to the RNC’s claim that they will not deliver the loyalty pledge to candidates until they qualify for polling and donor thresholds, Hurd told ABC: “I’m not in the business of lying to the American people for the sake of a microphone. I fully intend to get to 40,000 donors, meet the polling threshold, and show up to Milwaukee for the debate. I will not sign a pledge to any political leader, so go to my website and donate to see what the RNC does on August 23rd.”

Meanwhile Trump’s chief primary rival, Florida Gov. Ron DeSantis, said earlier this month that he would “respect the outcome of the process” but stressed that he intended to win.

“I think I’m going to be the nominee,” he said. “No matter what happens, I’m going to work to beat Joe Biden.”

ABC News’ Libby Cathey, Will McDuffie and Rachel Scott contributed to this report.

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