In an interview with CNN's Jake Tapper on "State of the Union," Rubio said Trump "has turned the most important election in a generation into a circus, into a complete fiasco and a carnival."
Tapper asked: "Would I be overstating matters if I said you sound like you're actually concerned that somebody -- before this is all over -- somebody might lose their life?
Rubio said: "I'm very concerned about that. We don't know what's going to happen next here. I know that we've reached the point where people in American politics have decided that if they don't agree with you, they can get angry at you, that you're a bad and evil person, that they can say anything they want about you."
"I think that all the gates of civility have been blown apart. We've now reached a point where everyone on both sides everyone is just saying or doing whatever they want, and you know, you can't just say or do whatever you want," he said. "This is not about political correctness. This is about rules of civility and the way a society talks to each other."
Rubio suggested he's considering backing off his pledge to support the Republican nominee if Trump wins the nomination.
"It's getting harder every day to justify that statement to myself, to my children, to my family, and to the people that support me," Rubio said. "This country deserves better. At some point, people have to wake up here. This is really going to do damage to America."
But the Florida senator defended Trump over the chaos in Chicago Friday night, saying that "some of these protesters that you saw in Chicago were obviously organized, maybe even paid, to disrupt the event."
He said Chicago's clashes between Trump supporters and protesters "looked like something out of the third world."
But he said liberals -- including supporters of Vermont Sen. Bernie Sanders, who Trump has blamed -- aren't entirely at fault.
"This is not just Bernie Sanders," Rubio said. "(Trump) wants to deflect and distract. Here's the bottom line: He has said to people, basically, beat up the protesters and beat up the hecklers and I'll pay your legal bills."
Rubio said he plans to stay in the presidential race past Florida's pivotal Tuesday primary, a winner-take-all contest.
But he said the repercussions of Trump's rise will haunt those involved in 2016's race.
"No matter what happens in this election, for years to come, there are many people on the right, in the media and voters at large that are going to have to justify how they fell into this trap," he said.