Presidential candidates Donald Trump and Ben Carson said Sunday that talk of a contested convention to select the Republican nominee violates terms of neutrality agreements they made with party leaders not to mount third-party campaigns.

Trump said party leaders need to “get used to” him being in the race, and he hopes that reports that Republican Party officials gathered recently to discuss contesting his nomination -- even if he receives the required number of delegates -- are incorrect.

“I’ve been hearing about these closed-door meetings and I don’t like that,” Trump told CNN’s “State of the Union With Jake Tapper.” “That wasn’t the deal I made. I signed a pledge, and the pledge was supposed to be a double deal. They were supposed to be honorable, so we’re going to find out. If it’s going to be that way we’ll have problems, but I hope it’s not going to be that way.”

The last so-called brokered convention in U.S. politics took place in 1952, when then-Illinois Governor Adlai Stevenson was drafted by the Democratic Party as a compromise candidate when no one else gained enough support to secure the nomination. Stevenson lost in the general election to Republican Dwight D. Eisenhower.

A crowded Republican field for 2016 with more than a dozen hopefuls has meant Trump, along with Carson, U.S. Senator Ted Cruz and others, have competed for a fractured party base.

‘Bit of a Maniac’

On “Fox News Sunday” the real estate mogul lashed out at Cruz, who has taken a 10-point lead over Trump among Iowa Republicans weeks before the state’s caucuses, according to a new Bloomberg Politics/Des Moines Register poll. Trump said Cruz doesn’t have the right temperament or the right judgment to be president, and has acted in the Senate “like a little bit of a maniac.”

Carson, a retired neurosurgeon who’s also shown a strong early presence in the race for the party’s nomination, renewed his threat to leave the party if a brokered convention designed to blunt his standing were to take place.

“One of the reasons that I got into this is because I heard the frustration in the people who are so tired of back room deals, of subterfuge, of dishonesty,” Carson said during an appearance on ABC’s “This Week with George Stephanopoulos.” “And, you know, if that is the case, then, you know, I’m out of here.”

The political novice spoke at a time his popularity among likely Republican voters has slipped. Carson was third in the Iowa poll behind with 13 percent support. An average of recent national Republican surveys by Real Clear Politics showed Carson running a close fourth behind Trump, Cruz and Florida Senator Marco Rubio.

‘Jury Is Out’

The Washington Post reported Thursday that 20 Republican party stalwarts discussed the possibility of brokering the convention at a Washington dinner held by Republican National Committee Chairman Reince Priebus. A person who attended the dinner confirmed to Bloomberg that it took place, and that Priebus, members of Congress, establishment lobbyists and others have held similar discussions for weeks.

Carson said he’s spoken to Priebus and was told that the meeting was a routine one and there are no back-room deals taking place. “But, you know, the jury is out. We’ll certainly be keeping a close eye on things,” he said.

The Republican establishment’s participation in a bid to thwart Trump comes a little more than three months after the billionaire signed a loyalty pledge presented to him by Priebus. Carson told ABC News Friday he has “no intention of running as an independent” but said he doesn’t “want to be a part of corruption.”

Trump said he agrees with Carson’s positions and sent him a note this week saying so.

Independent Run?

Establishment Republicans fear a Trump nomination would cause the party to lose the election and possibly seats in Congress, because he has advocated controversial positions such as rounding up and deporting millions of undocumented workers and a temporary ban on Muslims entering the U.S. A USA Today/Suffolk University poll released on Dec. 8 showed that 68 percent of Trump’s supporters would vote for him if he broke from the party and ran as an independent.

Trump said on Fox News that party leaders will need to get used to his presence. “I’m supposed to be on the other side writing checks,” he said. “Sorry I did this to you, but you’re going to have to get used to it.”

(An earlier version of this story corrected the spelling of Reince Priebus.)

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