CINCINNATI (AFP) - Donald Trump doubled down Sunday on his claim that "thugs" - not his heated rhetoric - are to blame for spiralling violence at his rallies, two days before crucial votes that could propel him to an insurmountable lead in the Republican White House race.
Trump hit the campaign trail again Sunday as a climate of growing tension engulfed the 2016 election race, with White House rivals on both sides of the political divide warning the Republican's inflammatory language was inciting violence.
A campaign rally in Chicago late Friday had to be cancelled because of unrest that saw ardent Trump supporters and opponents come to blows, after dozens of campaign stops where Trump has berated his opponents and encouraged the crowd to verbally and physically mistreat protesters.
The billionaire's invective also has targeted journalists, the disabled, women, Muslims, Hispanics and other minorities - often to raucous approval from thousands of chanting partisans.
But as with each new controversy swirling around the brash billionaire, Trump seemed unscathed by the furor, with polls suggesting he remained on a glide path toward the party nomination heading into Tuesday's make-or-break round of voting.
Dubbed "Super Tuesday 2" by US media, the latest key date in the run up to November's general election will see Democratic and Republican contests in the states of Florida, Ohio, Illinois, Missouri and North Carolina.
Trump this weekend jetted on his private plane between rallies in the delegate-rich states, as his Republican rivals Texas Senator Ted Cruz, Florida Senator Marco Rubio and Ohio Governor John Kasich also ramped up campaigning on the ground.
In Cincinnati, Ohio hundreds had already lined up in the early morning to see the candidate despite a persistent drizzle - while demonstrators also massed ahead of the event, chanting "Build bridges, Not walls" and "No Trump no KKK, no fascist USA." Some Trump supporters verbally challenged the protesters, but the event so far remained violence free.
Politicians across the spectrum are increasingly alarmed at the divisiveness and the erosion of civility seen in the campaign and have called on Trump to tone down his rhetoric, saying he is fanning division by exploiting anger among the electorate.
Senator Rubio, who is trailing in third place and like Kasich faces a make-or-break test in Tuesday's vote 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," he told CNN, "we're going to lose our republic."
Rubio doubled down on his warning that it was "getting harder every day" to imagine backing Trump if he wins the nomination, but added: "At the end of the day, I do not believe Donald Trump will be our nominee. I'm going to do everything I can to keep that from happening."
Trump has rejected out of hand any suggestion that his rhetorical excesses might have egged on the the escalating violence.
"I don't accept responsibility. I do not condone violence in any shape," he told NBC on Sunday, repeating his assertion that agitators - mostly linked to Democratic candidate Bernie Sanders - were responsible for the tensions spilling over.
"Bernie Sanders is lying when he says his disruptors aren't told to go to my events. Be careful Bernie, or my supporters will go to yours!" he taunted on Twitter.
Sanders denied his campaign had directed supporters to protest at Trump rallies.
"Trump's words must be taken with a grain of salt because I think as almost everyone knows, this man cannot stop lying about anything," the Vermont senator said to CNN. "People are catching on to Donald Trump. That's why he's getting reckless."
Trump explained away one particularly striking act of violence, when a supporter at a rally in North Carolina sucker-punched a demonstrator who was being led by police last week from a rally in North Carolina.
"I will tell you, from what I saw the young man stuck his finger up in the air and the other man sort of just had it. But I still I don't condone violence," he told NBC's Meet the Press programme, adding: "I have instructed my people" to look into paying the belligerent supporter's legal bills.
Early Saturday a demonstrator tried to rush on stage during Trump's rally in Dayton, Ohio, leading the candidate to claim the man was linked to the Islamic State in Iraq and Syria group - an assertion that he refused to disown on Sunday, despite it becoming apparent it was based on a crude video hoax.
"What do I know about it?" he told NBC. "All I know is what's on the Internet."