Ted Cruz fells long-time Republican frontrunner Donald Trump and Democrat Hillary Clinton was battled into a virtual tie with rival Bernie Sanders on Monday, as Iowans held the inaugural vote of the 2016 White House race.

Republican presidential candidates spar over national security issues and how best to counter the so-called Islamic State (IS) in the first debate since attacks in California and Paris.

DONALD Trump, one of the several Republican party candidates vying for the next US presidency, is in trouble.