CLEVELAND: Hundreds of police officers, Secret Service agents and private security guards in cars, on foot and on horseback blanketed the area around Donald Trump's campaign rally Saturday afternoon.

Dozens of protesters would soon be ejected from the event. And that was the calmest rally in the past several days thrown by the front-runner for the Republican presidential nomination.

Welcome to Trump's new normal.

After months spent goading protesters and appearing to encourage violence, Trump has seen his raucous rallies devolve over the past two weeks into events at which chaos is expected.

The real estate mogul is routinely unable to deliver a speech without interruption, and a heavy security presence is commonplace amid increasingly violent clashes between protesters and supporters.

On Friday, groupings of well-organised students succeeded in keeping Trump from even taking the stage at a rally in Chicago.

The next morning, a protester rushed the stage at a Trump rally outside of Dayton, forcing Secret Service agents to leap on stage and form a protective circle around him.

"Frankly, I'm a little shocked that we got to this point, I'm shocked at it," said Ohio Gov John Kasich, who is vying with Trump to win his home state's winner-take-all primary on Tuesday. "We cannot create in this country a toxic environment where images of people slugging it out at a campaign rally, think about it, are transmitted all over the globe," he said.

Trump's events have always been intense. For months, he incorporated interruptions by protesters into his speeches, growling "Get 'em out!" ─ sparking explosive cheers from the audiences as he did so.

While Trump sometimes appears angered by the disruptions, he has also embraced them, using the interruptions as opportunities to lead his supporters in chants of "USA, USA".

He's also joked about how the protesters force TV cameras to pan out over the crowd and show how large they are. But the confrontations began to escalate this month, most notably at a Trump event in New Orleans.

A steady stream of demonstrators interrupted Trump's speech, including a huddle of Black Lives Matter activists, who locked arms and challenged security officials to remove them.

There were skirmishes throughout the speech, mostly pushing and shoving, although one man was captured on video biting someone.

This week, an older white Trump supporter was caught on video punching a younger African-American protester as police led the protester out of a rally in North Carolina.

The supporter, later charged with assault, told an interviewer the next time he confronted a protester, "We might have to kill him."

Two days later, police arrested nearly three dozen people at a rally in St. Louis that was interrupted so many times by protesters that Trump joked about how long it was taking him to complete his remarks.

Hours before Trump was scheduled to appear Friday night at the University of Illinois at Chicago, the atmosphere inside a campus arena was crackling as protesters and supporters shouted back and forth, arms raised and yelling in each other's faces.

Some of the protesters, many of whom said they supported Democratic candidate Bernie Sanders, said they planned to rush the stage when Trump came out to speak. They didn't get the chance, as Trump called off the rally before even getting to the venue.

"It feels amazing, everybody came together," said Kamran Siddiqui, 20, and a student at the school. "That's what people can do. Now people got to go out and vote because we have the opportunity to stop Trump."

The next morning, Trump was mid-speech when a man, later identified by authorities as Thomas Dimassimo of Fairborn, Ohio, jumped a barricade and rushed at Trump. He was able to touch the stage before he was tackled by security officials. Trump initially laughed it off, but later in the day, said Dimassimo had ties to the militant Islamic State group.

Experts who watched a video Trump tweeted as evidence called the allegation "utterly farcical".

"Trump's accusations about it being linked to ISIS serve only to underline the totality of his ignorance on this issue," said Charles Lister, a fellow at the Middle East Institute.

At the Cleveland rally, more than a dozen officers on horseback patrolled the outside as police helicopters buzzed overhead. Hundreds of officers massed inside to block some exits and sweep the audience out after the event ended.

More than 50 protesters, including a pair of doctors who removed sweat shirts to reveal white T-shirts printed with "Muslim Doctors Save Lives in Cleveland", were told to leave.

Things weren't much different at Trump's evening rally in Kansas City, Missouri, where protesters interrupted the candidate throughout his speech. While he asked his supporters not to hurt them, a visibly annoyed Trump also said he was "going to start pressing charges against all these people".

Back in Cleveland, Brandon Krapes said he was punched repeatedly after he held up his sign, which said, "Trump: Making America Racist Again". His 17-year-old son Logan had a freshly bruised cheek from what he said was a punch in the face he received while trying to help his father.

"The sheer amount of hatred in there is so blatant, and Trump does nothing to stop it," said Sean Khurana, a 23-year-old Cuyahoga Community College student, who is Indian-American.

He said someone called him "ISIS" as he stood in line. "He provokes it."

Trump, meanwhile, celebrated a successful campaign day on Twitter. "Just finished my second speech," he wrote. "20K in Dayton & 25K in Cleveland- perfectly behaved crowd. Thanks ─ I love you, Ohio!"