US Republican presidential front runner Donald Trump, hunting for votes in three states ahead of a crucial round of nominating contests, has dismissed outbreaks of violence at his campaign events as "a little disruption".
Trump, who made appearances in North Carolina, Florida and Ohio before Tuesday's primaries, said the establishment Republicans who have laboured to stop his outsider candidacy needed to recognise his strength and rally to his cause.
"What they have to do is embrace this phenomenon and go with it. Let's go win," Trump said of party leaders at a rally in Hickory, North Carolina, where he was interrupted several times by protesters.
Trump rejected suggestions his combative campaign tone was to blame for recent clashes at his rallies, including one last week where a protester was punched and a Chicago rally that was cancelled after fights between Trump supporters and opponents.
He said the level of violence was inflated by the media and "basically" no one had been hurt at his rallies, although "maybe somebody got hit once".
"It's a little disruption, but there's no violence," Trump said, describing his campaign as "a movement and a lovefest".
Five states - Florida, Ohio, Illinois, North Carolina and Missouri - hold nominating contests on Tuesday for the November 8 election to succeed Democratic President Barack Obama.
Trump could seize control of the Republican race with a sweep and possibly knock out two of his rivals, Ohio Governor John Kasich and US Senator Marco Rubio of Florida.
Opinion polls show him leading in all five states except Ohio, where he is in a tight race with Kasich.
"If we win Ohio and we win Florida, then everybody agrees it's pretty much over," Trump told an afternoon rally in Tampa, Florida. "The Republican Party has to come together."
But the party's anti-Trump forces, including a Super PAC formed to oppose him, kept up their assault on the brash New York billionaire.
The Super PAC released an ad on Monday featuring demeaning quotes by Trump about women, and urged people to oppose him "if you believe America deserves better".
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Democratic presidential front runner Hillary Clinton also kept an eye on Trump, saying at a campaign event in Chicago that "I don't think the stakes have ever been higher, or the rhetoric on the other side ever been lower."
Her voice hoarse, Clinton said it was "time for us to unite as a country".
Clinton, a former secretary of state, hopes to pull away from Sanders, a US senator from Vermont, in Tuesday's voting. Polls gave her a big lead in Florida and North Carolina, but showed Sanders gaining ground in Ohio, Illinois and Missouri.
White House spokesman Josh Earnest criticised Trump's Republican rivals for declaring they would back him if he wins the party nomination for the November election.
"At some point, somebody in the Republican Party's going to have to step up and show some leadership," Earnest said.
Former Alaska Governor Sarah Palin, who appeared ahead of Trump in Tampa on Monday, said protesters were "trying to take away your rights" to gather peacefully.
"What we don't have time for is for all that petty, punk ass thuggery stuff that has been going on," she said, before she headed home to be with her husband, Todd, who was injured in a snowmobile accident.
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