Trump, other White House hopefuls face huge test Tuesday

United States - Americans in five major states prepared to vote Tuesday in make-or-break presidential nominating contests, with Donald Trump seeking to tighten his grip on the Republican mantle as rivals and critics bemoaned a weekend of campaign trail unrest.

Dubbed "Super Tuesday 2" by US media, the latest major date in the run-up to November's election will see Democratic and Republican primary contests in the states of Florida, Illinois, Missouri, North Carolina and Ohio.

"I love you Ohio. You can make the difference!" Trump said at an evening rally at the Youngstown airport, as he suggested the Midwestern state, widely seen as a microcosm of America, was his closest race of the five where delegates are up for grabs Tuesday.

But violent clashes and protests at Trump rallies over the weekend dominated US headlines, with rivals in both parties accusing the billionaire real estate mogul of creating a toxic campaign environment.

The latest polls nevertheless showed the Republican frontrunner in a position to win the Tuesday contests, although Ohio's Governor John Kasich holds a narrow lead in his state in some surveys.

A Kasich victory in Ohio may be the last chance to derail Trump's march to July's Republican nomination, especially as Tuesday marks the point when the party moves to a winner-takes-all format in terms of the delegates accorded for each primary win.

Trump struck a blue-collar tone as he urged Ohio to rejected their popular governor, saying he was better positioned to re-invigorate the state's struggling economy than Kasich.

"Your steel industry is dead," Trump said. "I'm going to bring your industry back." Florida, Illinois and Ohio are the day's biggest prizes for both parties, as each state offers large delegate hauls.

On the Democratic side, frontrunner Hillary Clinton is poised to extend her lead over rival Bernie Sanders, if polls prove accurate.

She is handily ahead in Florida, but Ohio appeared to be a tougher contest, where the former secretary of state only held a five-point lead, according to the latest Quinnipiac University poll released Monday.

Sanders, appealing to blue collar voters, has made impressive gains in the state, after trailing by as much as 30 points in polls last month.

In a sign of the stakes involved, Trump cancelled a rally Monday in Florida, where he has a 20-point lead over Marco Rubio, the US senator from the Sunshine State, to make a final pitch in Ohio.

Campaigning with Kasich on Monday was Mitt Romney, their party's 2012 nominee, who has tried to mobilize his party against Trump.

Also campaigning in Ohio was Sanders, who drew about 2,000 people at a rally in Youngstown where he slammed what he called "disastrous" US trade policies over the past 20 years that he said had cost America "millions of decent paying jobs." "If we have a good vote, and people come out, we're going to win in Ohio," said Sanders, 74.

The clashes that erupted at Trump's Friday rally in Chicago marked an escalation in tensions that have trailed the controversial candidate.

Protesters turned up at his rally in Hickory, North Carolina Monday, but this time, he patiently waited for their chants to subside.

"There's no violence," he said. "It's a movement, it's a love fest." He acknowledged there was "anger from all sides including from our side" but added: "We're not angry people. We're all good people. There's anger at the incompetence." Nevertheless, Trump's invective against immigrants, Muslims and Hispanics have become a staple of his campaign, drawing roars of approval from supporters but also increasingly aggressive protests.

On Saturday, a protester rushed the stage as Trump was winding up a speech near Dayton, Ohio.

"I was thinking that Donald Trump is a bully, and he is nothing more than that," Thomas DiMassimo, a 22-year old college student who was charged with disorderly conduct and inciting panic, told CNN.

Trump has rejected out of hand any suggestion that his rhetorical excesses have created a climate of violence, blaming Sanders supporters for sowing trouble - and threatening to respond in kind by sending supporters to picket the Democratic candidate's rallies.

The Vermont senator responded bluntly at a CNN Democratic town hall event: "Donald Trump is a pathological liar." Clinton, campaigning in Chicago Monday, has accused the Republican frontrunner of engaging in "political arson" and "trafficking in hate and fear." "I am so worried about our country and what could happen if we don't band together to elect a president that can represent all of America," she said.

Trump's Republican rivals also seemed shaken by the ugly turn in a campaign that has for months endured mudslinging and name-calling.

Rubio, who like Kasich faces a do-or-die test Tuesday in his home state, called Trump's language "dangerous." "If we reach a point in this country where we can't have a debate about politics without it getting to levels of violence and anger," Rubio told CNN, "we're going to lose our republic."