Presidential candidates are criticizing Donald Trump's "ugly" rhetoric after safety concerns forced the billionaire real estate mogul to postpone a rally at the University of Illinois-Chicago that had drawn thousands of vocal protesters.

Ted Cruz said violent protests are "the predictable consequence" of the atmosphere Trump's campaign has created, while Bernie Sanders had his own strong words for the Republican presidential candidate. Both spoke at previously scheduled engagements in the Chicago area, with the Illinois primary set to play a pivotal role in both parties' nominations on Tuesday.

Cruz, speaking at a dinner for Illinois Republicans, told a gaggle of reporters that the scenes at the UIC Pavilion are likely to be repeated, given the environment the Trump campaign fosters.

"I think a campaign bears responsibility for creating an environment – when the candidate urges supporters to engage in physical violence, to punch people in the face, the predictable consequence of that is that it escalates," Cruz said. "And today is unlikely to be the last such instance."

Florida Sen. Marco Rubio said "it shouldn't surprise us that you see this violence" at a Trump rally and called on his Republican rival to take responsibility for the violence.

"And I do think Donald needs to realize and take responsibility for the fact that some of the rhetoric he has used could potentially be contributing to this environment that is growing increasingly disturbing for a growing number of Americans," Rubio said Friday evening. [[371875122, C]]

Asked Saturday morning before an event in Florida if he'd support the republican nominee, Rubio said he "didn't know," adding that he still intended to but "it's getting harder every day."

Ohio Gov. John Kasich said that some people "let their opposition to [Trump's] views slip beyond protest into violence," but added that we can't let that happen again.

"The seeds of division that Donald Trump has been sowing this whole campaign finally bore fruit, and it was ugly," Kasich added.

Democratic presidential candidate Hillary Clinton called for members of both parties to "loudly and clearly" condemn the violence in politics.

“The divisive rhetoric we are seeing should be of grave concern to us all. We all have our differences, and we know many people across the country feel angry... we should use our words and deeds to bring Americans together," Clinton said in a statement.

Sanders responded to the violence at the rally in an exclusive interview with NBC Chicago.

"What I hear is, I think what the American people see on television is supporters of his actually, physically hurting people who are protesting," Sanders said.

Chicago Police brawl with protesters outside UIC Pavilion after Trump cancels rally. Sky 5 reports.

Trump took to Twitter early Saturday and blamed organized "thugs" for the clashes that forced him to call off the chaotic rally in Chicago where supporters and protesters broke into fights even before the controversial candidate took the stage.

"The organized group of people, many of them thugs, who shut down our First Amendment rights in Chicago, have totally energized America!" he tweeted. [[371876962, C]]

A defiant Trump continued to address the cancellation of his Chiago event while speaking at a campaign rally in Dayton, Ohio, Saturday morning. Trump defended his supporters, who he called "very nice people" and said the decision was made in order to stop a "planned attack" by a group of "professional people."

Chicago Police said five people were arrested amid the chaos. Additionally, two CPD officers were injured — both non life-threatening — though one officer was struck on the head by a bottle. [[371840161, C]]

President Obama, at a Democratic fundraiser in Austin, Texas, also condemned Trump and Republicans on Friday, although his comments came about an hour before the rally was supposed to begin.

Obama joked about the Republican establishment being shocked that Trump would be "fanning anti-immigrant sentiment or anti-Muslim sentiment."

"How can you be shocked?" Obama continued. "This is the guy, remember, who was sure that I was born in Kenya."