Mr Trump called off a rally on Friday night in Chicago after clashes between protesters and supporters.
The Republican who has won a string of primary contests has blamed the supporters of Democrat Bernie Sanders and denied responsibility for the violence. On Sunday, he said his campaign is "not provoking" and "wants peace".
He said no one gets hurt at his "love-fest" rallies.
A Quinnipiac University poll shows that Mr Trump is leading the way in Florida and tied with Ohio Governor John Kasich in Ohio ahead of crucial state primaries on Tuesday.
Here's what people are saying about Mr Trump and the violence at his rallies:
What Trump says about protesters at his rallies
Democratic candidate Bernie Sanders: Called Mr Trump a "pathological liar" after he said he had sent protesters to disrupt his rallies.
Florida Senator Marco Rubio: Said it is "harder every day to justify" backing Mr Trump should he win the Republican nomination and said conservatism is not about "how angry can you get, how offensive you can be, how loud you can speak".
Ohio Governor John Kasich: Asked his staff to make a list of Mr Trump's quotes promoting violence at his rallies and that Mr Trump's "toxic" tone makes it even more important for him to win his home state in the primary election on Tuesday.
Senator Ted Cruz: Said that the culture of violence is Mr Trump's fault, telling reporters that "any candidate is responsible for the culture of the campaign".
New York City Mayor Bill de Blasio: Tweeted that there is no question Mr Trump a racist.
Democratic candidate Hillary Clinton: Said Mr Trump's campaign consists of "hate" and "fear".
President Barack Obama:  Said over the weekend: "Our leaders - those who aspire to be our leaders - should be trying to bring us together and not turning us against one another and speak out against violence and reject efforts to spread fear or turn us against one another. And if they refuse to do that, they don't deserve our support."
House Speaker Paul Ryan: Said the violence at Mr Trump's rallies is "very concerning" and that candidates must take "responsibility for the environment" at their events
Neurosurgeon Ben Carson, former Republican candidate: Told NBC's Today programme that the violence could get worse, placing blame on the protesters, saying "I think certainly if the protesters continue with their... tactics, there is a real possibility of escalation".
Former Arkansas Governor Mike Huckabee: Defended Mr Trump, condemning the Chicago protesters. "I think it's ridiculous to blame Trump for a bunch of thugs out on the street," he told the Huffington Post.
Conservative pundit Ann Coulter:Tweeted that "left-wing fascists violently shut down a peaceful Trump rally last night & Cruz + the entire media took the animals' side"
Presidential candidates for the 2016 race and other politicians are speaking out against Donald Trump after a string of violence at his rallies.