Eric Thayer/Reuters Donald Trump and RNC Chair Reince Priebus are calling on Trump's former rivals to stand by an ill-advised pledge.

WASHINGTON ― The GOP pledge to which party chairman Reince Priebus is demanding fealty from the likes of Jeb Bush and John Kasich is the same pledge that presidential nominee Donald Trump repudiated earlier this year.

“Those people need to get on board,” Priebus told CBS’s “Face the Nation” on Sunday. “If they’re thinking they’re going to run again someday, you know, I think that we’re going to evaluate the process of the nomination process, and I don’t think it’s going to be that easy for them.”

Trump chimed in Monday, suggesting that the former Florida governor and the current Ohio governor entered into a binding contract, which they are now violating by refusing to endorse him.

“And the contract is so clear. It’s so clear. It said, ‘I will endorse’ the person that wins the primaries, right? And not only did I win, I got 14 million votes,” Trump said during a phone interview with Fox News. “These people all want to run in four years, right? If I were head of the Republican Party, I’d say you can’t do it!”

Neither Trump nor Priebus, of course, brought up Trump’s own declaration on March 29 ― when it appeared many in the party establishment were trying to block the real estate mogul from getting the nomination ― that he was no longer bound by the pledge.

“I have been treated very unfairly ... by basically the RNC, the Republican Party, the establishment,” Trump said at a CNN town hall event back then.

John Weaver, a top political adviser to Kasich, said Monday that Trump had been even more cavalier in earlier statements. “He also said if he wasn’t the nominee, he wouldn’t honor it,” Weaver said. “That pledge? Yeah.”

Neither the Republican National Committee nor Trump’s campaign responded to Huffington Post queries on the topic.

Matt Borges, chairman of the Ohio GOP who is both loyal to Kasich and trying to help the Republican nominee carry the state, said he did not understand why Priebus and Trump are making an issue of this now.

“I think the governor is pretty clear about where he is at this point in time. I don’t see that changing,” Borges said. “John Kasich is the most popular elected official in Ohio. To go out and pick a fight with the guy with just 50 days to go just makes no sense.”

As to punishing Kasich, Bush and other 2016 GOP candidates who fail to endorse Trump, Weaver said that might be a question for voters in the future, but not for the RNC chairman.

“There’s no such rule that a party candidate can be penalized for something that’s happened in the past,” Weaver said, adding, “Otherwise he wouldn’t be the nominee. He donated to Clinton.” (Trump and his oldest son donated repeatedly to Hillary Clinton when she was a New York senator.)

The fact the pledge exists at all is testament to how much Republican leaders feared a third-party run by Trump at a time when they didn’t see him as a realistic threat to win the nomination. They believed Trump could self-fund an independent White House bid from his personal fortune, despite numerous published analyses over the years suggesting he was worth far less than his purported “$10 billion” net worth.

At the first GOP presidential debate in August 2015, Trump was the sole candidate on stage to raise his hand when moderator Brett Baier asked who would not promise to back the ultimate Republican nominee and to refrain from running as an independent.

“If I’m the nominee, I will pledge I will not run as an independent,” Trump said. But he was unwilling to say what he would do if he didn’t win the nomination. He then suggested he could use the offer of his support as a bargaining chip: “I’m, you know, talking about a lot of leverage.”

In response, the RNC drew up a written pledge for its candidates to sign promising to support the eventual nominee. Priebus took a copy to Trump at Trump’s Manhattan office to collect his signature in person ― an action that critics fear forever altered the power relationship between the party and the reality TV host-turned-presidential candidate.

Editor’s note: Donald Trump regularly incites political violence and is a serial liar, rampant xenophobe, racist, misogynist and birther who has repeatedly pledged to ban all Muslims — 1.6 billion members of an entire religion — from entering the U.S.