Just days before a key set of primaries in the race for President, Donald Trump and his supporters found themselves under attack in both parties, after security concerns prompted Trump to cancel a rally in Chicago on Friday night.

"Tonight the seeds of division that Donald Trump has been sowing this whole campaign finally bore fruit, and it was ugly," said John Kasich, as he urged people to resist the temptation for violence.

Like Kasich, Marco Rubio took aim at Trump, charging that Trump's tough words have divided the nation, saying "words have consequences."

Also joining in was Ted Cruz, as he told Fox News that Trump has been wrong to encourage retaliation against demonstrators at Trump rallies.

As for Trump, he made the rounds on the cable TV networks by phone last night to defend himself, as he argued the real problem was presented by the protesters, not his supporters.

More liberal groups also got in on the controversy.

"Mr. Trump and the Republican leaders who support him and his hate-filled rhetoric should be on notice after tonight’s events," said Ilya Sheyman, the executive director of MoveOn.org.

"To Donald Trump, and the GOP, we say, welcome to the general election," Sherman added in a statement.

Without directly criticizing Trump, Hillary Clinton also got in a jab at the GOP leader, saying the "divisive rhetoric we are seeing should be of grave concern to us all."

Trump has events on Saturday in Dayton, Cleveland and Kansas City.