Fresh off three more primary victories, Donald Trump vowed Wednesday to blow off the next Republican presidential debate and warned of “riots” if power-brokers deny him the nomination at the convention even if he's leading in the delegate count.

The billionaire New York developer, who held a narrow lead in Missouri and lost Ohio on Tuesday, is faced with the prospect of a floor fight at the party convention in July if he's leading in delegates but falls short of a majority, 1,237.

“I think we’ll win before getting to the convention, but I can tell you, if we didn’t and if we’re 20 votes short or if we’re 100 short and we’re at 1,100 and somebody else is at 500 or 400 cause we’re way ahead of everybody, I don’t think you can say that we don’t get it automatically,” Trump said on CNN on Wednesday. “I think you’d have riots.”

“I wouldn’t lead it, but I think bad things would happen,” Trump said, adding the outcome would “disenfranchise” his supporters.

Trump's decision to skip the debate, and a subsequent announcement by Ohio Governor John Kasich that he would join Trump’s boycott, led Fox News to cancel the debate set for Monday in Salt Lake City. Trump claimed to have been caught off guard by the event. “We’ve had enough debates,” he said on the network Wednesday. “Nobody told me about it and I won’t be there.” He said skipping the debate would allow him to speak at the American Israel Public Affairs Committee policy conference running from Sunday to Tuesday in Washington.

Kasich, who won his home state's primary on Tuesday, said he wouldn't take part in the debate if Trump wasn't there, according to a top aide, John Weaver. Representatives of Texas Senator Ted Cruz didn't immediately return telephone calls seeking comment.

Trump skipped the debate held days before the Iowa caucuses on Feb. 1 that were won by Cruz. Trump had complained about Fox News’ treatment of him at the time, and instead held an event that he said raised money for veterans’ charities. Utah holds its Republican caucuses on March 22.

“On Feb. 20, the Republican National Committee announced that a GOP presidential primary debate would be held on March 21 in Salt Lake City,” the network’s executive vice president of news, Michael Clemente, said in a statement. “They offered that debate to Fox News Channel to host, provided there were enough candidates actively campaigning. This morning, Donald Trump announced he would not be participating in the debate. Shortly afterward, John Kasich's campaign announced that without Trump at the debate, Kasich would not participate. Ted Cruz has expressed a willingness to debate Trump or Kasich—or both. But obviously, there needs to be more than one participant. So the Salt Lake City debate is cancelled.”

Kasich deprived Trump of a sweep on Tuesday by winning the Buckeye State. Senator Marco Rubio ended his campaign for the Republican nomination after getting beaten badly by Trump in Florida.

On the Democratic side, former Secretary of State Hillary Clinton defeated Vermont Senator Bernie Sanders in four of five contests and held a narrow lead in Missouri, a race the Associated Press said was too close to call. Her victory speech made clear she is increasingly focusing on a general-election race against Trump in the fall.

Andre Tartar/Bloomberg

Cruz, who says he intends to win 1,237 delegates before the convention, noted in a CNN interview that if he falls short, delegates will have discretion on whom they vote for.

Cruz strategists have been gaming scenarios in which they pick off delegates to keep Trump from clinching the nomination in Cleveland. If no candidate gets to the convention with a majority, Cruz could try to flip delegates pledged to Rubio, Kasich, and other candidates on the second ballot. Forty-four states allow a state party convention or executive committee to assign delegates to their preferred candidates.

Kasich is banking on the possibility of convention rules being rewritten when the delegates arrive, allowing him to compete there. (He's not expected to win the number of states required to appear on a convention ballot under current rules.) But with the majority of delegates already claimed by Trump and Cruz, they may be unwilling to give Kasich a chance.

“The Cruz folks would never allow the rules to be changed and of course we wouldn't either,” said Barry Bennett, a Trump convention strategist, according to Politico.

The possibility of a chaotic convention even led former House Speaker John Boehner on Wednesday to say he'd hypothetically support his successor, Paul Ryan, as nominee, despite voting for Kasich in the Ohio primary. Ryan has said he isn’t interested.

“If we don’t have a nominee who can win on the first ballot, I’m for none of the above,” Boehner said at a conference, according to Politico. “They all had a chance to win. None of them won. So I’m for none of the above. I’m for Paul Ryan to be our nominee.”

“He has endorsed Governor John Kasich,” Boehner spokesman David Schnittger said in an e-mail. “His off-the-cuff comments this morning were about a hypothetical scenario in which none of the current candidates are able to secure the nomination at the convention.”

Republicans haven't had a contested convention since 1976, when President Gerald Ford edged an insurgent Ronald Reagan.

Trump led with 460 delegates heading into Tuesday’s elections, followed by Cruz with 370, Rubio with 163, and Kasich with 63, according to the Associated Press. By Wednesday morning, with the Missouri race still uncalled, Trump stood at 661, Cruz at 406, and Kasich at 142, according to the newswire.

Along with Utah, the next Republican contest is in Arizona on March 22. Arizona’s vote is a primary with 58 delegates and Utah’s is a caucus with 40. Arizona’s delegates, like most from other states, are free to vote for the candidate of their choice if no candidate enters the convention with a majority.

In both states, only registered Republicans will be eligible to vote. Ron Nehring, a spokesman for Cruz, said those rules favor the Texan.

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