WASHINGTON: Donald Trump warned Wednesday of riots if he is denied the Republican presidential nomination, after adding to his growing pile of primary wins but losing in the key state of Ohio. Trump and Democrat Hillary Clinton emerged from the “Titanic Tuesday” contests in five states as their respective parties’ clear frontrunners, but the billionaire real estate mogul’s failure to sweep the races means he may fall short of the delegates needed to win the Republican nomination outright. After the most divisive US campaign in nearly half a century, one that has shattered all rules of decorum and aroused an angry electorate, it remains unclear whether Trump can unite his party in time for the Republican convention in Cleveland in July. Top Republican powerbrokers are still maneuvering to derail Trump, seen as an outsider who hijacked the party primaries, and are looking to a so-called brokered convention — which can occur if no candidate wins a majority of delegates by June — as their likely last chance. But that extraordinary scenario — in which the party would seek to override the outcome of the primaries and unite around an alternative candidate — is a long shot few in the party seem to have the stomach for. “If Trump has hundreds more delegates than the runner-up… it will be exceedingly difficult to deny him the nomination.