Donald Trump and Hillary Clinton both took one step closer to securing nominations for the 2016 US presidential race with commanding victories on a night of caucuses dubbed "Super Tuesday".
The pair won seven caucuses each, shortening their odds of facing one another in the race for the White House.
Republican candidate Ben Carson has dropped out of the presidential race in the US elections.
The retired neurosurgeon said he did not see a "political path forward" after his rival Donald Trump and Democrat Hillary Clinton triumphed on Super Tuesday.
He is expected to give a final speech on Friday formally ending his campaign.
Republican presidential nominee front-runner Donald Trump has called Mitt Romney's attack speech "irrelevant".
Mitt Romney launches a scathing attack on Donald Trump, saying the mogul candidate lacks the temperament or judgement for the White House.
Senior members of the US Republican party have begun rallying against leading presidential candidate Donald Trump.