North Marion (Ohio): Republican presidential front-runner Donald Trump faced a last day of campaigning on Monday before a crucial round of nominating contests including in Florida and Ohio, where establishment Republicans worked to trip him up.
Trump supporters and protesters have clashed at his rallies in recent days, fueling accusations that the New York billionaire has created an ugly atmosphere with his campaign invective against groups such as Mexican immigrants and Muslims, and his rough tone toward hecklers.
Trump, who has rejected accusations he is to blame for the tensions, has emerged from the early nominating contests with a clear lead in the number of delegates needed to win the party nomination for the November 8 election.
He is trailed by Ted Cruz, a US senator from Texas, and could seize control of the race with big wins in Tuesday's voting in Ohio, Florida, Illinois, Missouri and North Carolina. Opinion polls also showed him with comfortable leads in all those states, except Ohio, where he is roughly tied with the state's governor John Kasich.
Kasich, trailing in the delegate count and seen as needing to win in his home state to stay in the race, was getting campaign help on Monday from Mitt Romney, who was the party's 2012 presidential candidate and who delivered a furious attack on Trump this month.
Trump, a real estate magnate and former reality television star, has fired up enthusiastic crowds with his promise to "make America great again." But he has bucked Republican orthodoxy on policies including free trade and offended a range of Americans with his calls to temporarily ban Muslims from the country and deport illegal immigrants.
In Florida, US Senator Marco Rubio, a favorite of the party establishment, has staked his survival in the campaign on winning in his home state. He has also suggested a tactical vote to stop Trump - encouraging his supporters in Ohio to cast their vote for Kasich.
Trump scheduled appearances in North Carolina, Ohio and Florida on Monday, after several days of events marked by outbreaks of shouting and shoving between supporters and protesters, who decry what they call his bigoted and divisive rhetoric.
Trump canceled a big rally in Chicago on Friday evening over security after protesters swarmed the event, sparking clashes. On Saturday, he was rushed by a man on an Ohio stage and repeatedly blamed Bernie Sanders, a candidate in the Democratic race, for the protesters' actions.
On the Democratic side, former Secretary of State Hillary Clinton has a decent chance to pull away from Sanders on Tuesday. But her loss to him last week in Michigan, which shocked pollsters who believed Clinton had a double-digit lead, underscores the left-leaning US senator's ability to surprise.
At a town hall on Sunday night, the two Democrats both devoted time to attacking Trump, who they say is inciting violence at his rallies, before getting down to their battle with each other.
It was unclear whether the tensions at his campaign events might hinder Trump's advance to the nomination to be the Republican candidate in November's election to succeed Democrat Barack Obama.
"It will help Trump among hard-core Republicans and hurt him among independents," said Frank Luntz, a Republican pollster.
"It will help him among those who resent the left and their protests and their disruptions. But it will hurt him among independents who don't like the chaos and the confusion.