AP Photo/Gerald Herbert

Republican presidential candidate Donald Trump speaks to supporters at his primary election night event at his Mar-a-Lago Club in Palm Beach, Fla., Tuesday, March 15.

WASHINGTON (AP) — An emboldened Donald Trump offered himself Wednesday as the inevitable Republican presidential nominee after his latest string of wins and called on balky GOP leaders to embrace the voters’ “tremendous fervor” for his candidacy. If GOP leaders try to deny him the nomination at a contested convention when he is leading the delegate count, Trump warned, “You’d have riots.”

Trump, who padded his delegate lead and won at least three more states in the latest round of voting, predicted he’d amass enough support to snag the nomination outright before the Republican convention — without much difficulty, in fact — and added that “there’s going to be a tremendous problem” if the Republican establishment tries to outmaneuver him at the convention.

Democrat Hillary Clinton, eager for a November matchup against Trump, took direct aim at him after strengthening her position against rival Bernie Sanders with another batch of primary victories of her own.

“Our commander-in-chief has to be able to defend our country, not embarrass it,” Clinton said in a speech that largely ignored Sanders. “We can’t lose what made America great in the first place.”

With anti-Trump Republicans frantically seeking scenarios to deny the billionaire businessman the GOP nomination, Trump suggested in a round of calls to morning TV shows that the party establishment already is starting to fall in line behind him. Without naming names, Trump said some of the same Republican senators who are publicly running him down have called him privately to say they want to “become involved” in his campaign, eventually.

Trump, devoting little attention to his two remaining GOP rivals, was ready for a head-on fight with Clinton.

He said she’d be “a major embarrassment for the country” and added that she “doesn’t have the strength or the stamina to be president.”

The GOP front-runner also said he’d skip a GOP debate scheduled for Utah on Monday, saying, “I think we’ve had enough debates.”

Clinton triumphed in the Florida, Illinois, Ohio and North Carolina presidential primaries, putting her in a commanding position to become the first woman in U.S. history to win a major-party nomination. Trump strengthened his hand in the Republican race with wins in Florida, North Carolina, and Illinois but fell in Ohio to that state’s governor, John Kasich. Votes were also being counted in Missouri, though races in both parties there were too close to call.

Kasich, celebrating his home state win over Trump, told NBC’s “Today” show, “I dealt him a very, very big blow to being able to have the number of delegates.” He added that neither Trump nor Texas Sen. Cruz can win the general election.

But after Tuesday’s contests, it’s mathematically impossible for the Ohio governor to win a majority of delegates before the GOP’s July national convention.

Even before Tuesday’s results, a group of conservatives was planning to meet to discuss ways to stop Trump, including a contested convention or rallying around a third-party candidate. While no such candidate has been identified, the participants in Thursday’s meeting planned to discuss ballot access issues, including using an existing third party as a vehicle or securing signatures for an independent bid.

A person familiar with the planning confirmed the meeting on the condition of anonymity because the person was not authorized to discuss the gathering by name.

Even House Speaker Paul Ryan, R-Wis., did not rule out the idea of being drafted by the party at the convention.

“People say, ‘What about the contested convention?'” Ryan said in an interview with CNBC. “I say, well, there are a lot of people running for president. We’ll see. Who knows?”

Trump said putting up a third-party candidate to block him would “guarantee” a Democratic win in November.

With more than half the delegates awarded through six weeks of primary voting, Trump is the only Republican candidate with a realistic path to the 1,237 delegates needed to clinch the nomination through the traditional route.

His message to the party: “There’s a tremendous fervor out there, and I think the Republicans, the leadership of the Republicans, should grasp it. Because you’re going to win in November if you take advantage of it.”

Ted Cruz is in better position than Kasich, but he too faces a daunting mathematical challenge after losing four of five contests Tuesday. The Texas senator needs to claim roughly 75 percent of the remaining delegates to earn the delegate majority, according to Associated Press delegate projections.

With Florida Sen. Marco Rubio out of the race, Cruz welcomed the Florida senator’s supporters “with open arms.” The fiery conservative tried to cast the GOP nomination battle as a two-person race between himself and Trump.

On the Democratic side, Clinton has at least 1,561 delegates, including the superdelegates who are elected officials and party leaders free to support the candidate of their choice. Sanders has at least 800. It takes 2,383 to win the Democratic nomination.

Trump’s Florida victory brought his delegate total to 621. Cruz has 396 and Kasich 138. Rubio left the race with 168.

AP writer Stephen Ohlemacher contributed to this report.