US Republican front-runner Donald Trump warned yesterday of riots if he was denied the party's presidential nomination after a string of victories in the primary elections.The outspoken New York billionaire scored big wins in primaries in Florida, Illinois and North Carolina on Tuesday, knocking out rival Marco Rubio and bringing him closer to the 1237 convention delegates he needs to win the nomination.But Trump lost the crucial state of Ohio and left the door open for those in the party trying to stop him from becoming the Republican nominee for the November 8 election.Trump might fall short of the majority required, enabling the party's establishment to put forward another name at the July convention in Cleveland at which the candidate is finally named.In an interview with CNN yesterday, Trump said the party could not deny him the nomination if he failed to win enough delegates."I don't think you can say that we don't get it automatically. I think you'd have riots. I'm representing many, many millions of people."While the Republican race became mired deeper in turmoil, Democrat Hillary Clinton won victories in Florida, Illinois, Ohio and North Carolina on Tuesday.The scale of her win has cast doubt on US Senator Bernie Sanders' ability to overtake her for their party's nomination.Republican Party leaders are appalled at Trump's incendiary rhetoric and believe his policy positions are out of step with core Republican sentiment, such as his vow to deport 11million illegal immigrants, temporarily ban Muslims from the US and build a wall along the border with Mexico to keep out illegal migrants.The Republican establishment's bid to stop Trump might have come too late. The field of candidates that once included him and 16 others has dwindled to only three with Trump, 69, in command ahead of US Senator Ted Cruz, 45, and Ohio governor John Kasich, 63, who won Ohio's Republican primary on Tuesday...