Republican presidential candidate Donald Trump said that "professional agitators" bore much of the blame for violence at his rallies.
His comments follow footage that shows a protester being beaten and another apparently being grabbed by the candidate's campaign manager.
Speaking on ABC's This Week on Sunday, Mr Trump defended campaign manager Corey Lewandowski and declined to condemn supporters who had attacked protesters at his increasingly chaotic rallies.
Nor did he back down from his warning of riots in the streets if, despite being the most popular candidate among Republican voters, the Republican Party denied him the nomination for the November election.
Senior figures in the party are openly plotting to prevent Mr Trump from becoming the nominee because they view him as insufficiently conservative, and Mr Trump was due to privately meet with some party leaders in Washington on Monday, the Washington Post reported.
"I don't know what's going to happen, but I will say this, you're going to have a lot of unhappy people," he said on This Week, predicting anger at the party's national convention in July should someone else end up the nominee.
"I don't want to see riots, I don't want to see problems. But you're talking about millions of people."
Scenes of mayhem have become increasingly common at the billionaire New York businessman's rallies, which have been frequently interrupted by protesters.
Many of the protesters are Democrats, who say Mr Trump's controversial remarks on immigrants and Muslims are dangerous.
The 69-year-old candidate has sometimes encouraged his supporters to use violence on protesters, and on at least one occasion said that he would like to punch a protester himself.
Television footage from an Arizona rally on Saturday showed a man punching and kicking a protester as he was led out of the event. Another video appeared to show Mr Lewandowski grabbing a protester by the back of his shirt.
Mr Trump declined to condemn the violence and said it was often provoked by protesters, who briefly blocked a highway leading to an Arizona rally on Saturday.
"These people are very disruptive people. They're not innocent lambs," he said.
He also defended Corey Lewandowski and said a security official had actually grabbed the protester. Mr Lewandowski also manhandled a reporter last week, according to the Washington Post.
"I give him credit for having spirit," Mr Trump said of Mr Lewandowski.
Republican leaders have said Mr Trump needs to more clearly discourage his supporters from engaging in violence.
About two dozen senior Republican figures will meet with Mr Trump at a law firm near the Capitol on Monday afternoon in what the Trump campaign described as an effort to improve "party unity", the Washington Post reported. The newspaper did not say who would be attending.
Candidates were also required to submit their most recent monthly financial disclosures to the Federal Election Commission on Sunday.
Hillary Clinton, the front-runner for the Democratic Party's nomination, raised $US30.1 million in February, according to filings, about $12m less than that raised by chief rival, US Senator Bernie Sanders of Vermont in the same period.
Mrs Clinton began March with $31m in cash on hand, according to filings.