Donald Trump's Rivals Blame Him for Creating 'Toxic Environment' at Campaign Events Amid violent unrest at campaign events, Trump's rivals are expressing concern.

 -- Following the violent confrontations between protesters and supporters of Republican presidential candidate Donald Trump at campaign events in Chicago and St. Louis on Friday, Trump’s rivals -- Republican and Democrat alike -- laid much of the blame for the clashes at his feet.

In a rare display of cross-party unity, Trump drew rebukes from all three of his remaining opponents for the GOP presidential nomination, the two Democratic contenders and even President Obama.

Speaking to reporters in Florida Saturday morning, Marco Rubio urged Americans to “look at the rhetoric coming from the front-runner in the presidential campaign.”

“This is a man who in rallies has told his supporters to basically beat up the people in the crowd and he will pay their legal fees,” the Florida senator and Republican candidate said, “someone who is basically encouraging the people in the audience to rough up anyone who stands up and says something he doesn't like.”

Meanwhile, Ohio Gov. John Kasich accused Trump of creating “a toxic environment that has allowed his supporters and those who sometimes seek confrontation to come together in violence.”

“There is no place for this,” Kasich said in Cincinnati, Ohio. "There is no place for a national leader to prey on the fears of the people who live in our great country.”

Friday night Texas Sen. Ted Cruz declared: “In any campaign, responsibility starts at the top.”

“Any candidate is responsible for the culture of the campaign,” he told reporters in Illinois. “When you have a campaign that disrespects the voters, when you have a campaign that affirmatively encourages violence, when you have a campaign that is facing allegations of physical violence against members of the press, you create an environment that only encourages this sort of nasty discord.”

The admonishments from his fellow candidates come at a moment of heightened tension between the Republican front-runner and protesters at his jam-packed campaign events. Last night, Trump postponed a planned event in Chicago over concerns about the safety of attendees and demonstrators. And at his first event of the day in Dayton, Ohio on Saturday, Secret Service agents were forced to come to Trump’s aide when someone appeared to be trying to reach the stage where he was speaking. At the event, Trump called the hostilities in Chicago a “planned attack" and a "disgrace."

Rubio, Kasich and Cruz noted that protesters also deserved their share of the blame.

Kasich said people went to Trump’s event in Chicago “with the purpose of causing that confrontation” adding, “To see Americans slugging themselves at a political rally deeply disturbed me.” And Rubio said, “You don’t have the right to disrupt an event just because you disagree with someone.”

Nevertheless, with Trump’s grip on the Republican nomination appearing to tighten, both Rubio and Kasich indicated that recent events had them questioning a pledge they made to support whoever is chosen to be their party’s nominee.

“It's getting harder every day,” Rubio said while Kasich suggested the violence of the last 24-hours “makes it extremely difficult” to support Trump.

Elsewhere on the campaign trail, Democratic presidential candidates Hillary Clinton and Bernie Sanders both tore into Trump on Saturday.

“You know, we will always have our differences, won't we? That's what happens in a democracy like ours,” Clinton said in St. Louis. “But the ugly, divisive rhetoric we are hearing from Donald Trump and the encouragement of violence and aggression is wrong, and it's dangerous.”

She added, “If you play with matches, you're going to start a fire you can't control. That's not leadership. That's political arson."

At a news conference in Chicago, Sanders called on Trump “to be loud and clear and tell his supporter that violence at rallies is not what America is about.”

And at a Democratic National Committee fundraiser in Texas on Saturday, President Obama, without mentioning Trump by name, counseled that “those who aspire to be our leaders should be trying to bring us together and not turning us against one another, to speak out against violence and reject efforts to spread fear or turn us against one another.”

“If they refuse to do that,” the president added, “they don’t deserve our support.”

ABC's Brad Mielke, Ben Gittleson, Jessica Hopper, Alex Mallin, MaryAlice Parks and Liz Kreutz contributed reporting.