Republican Donald Trump rolled to victory in South Carolina to solidify his status as the front-runner and Democratic presidential candidate Hillary Clinton beat back a strong challenge from Bernie Sanders in the Nevada caucuses.
Trump, who in the final days of the primary battle got entangled in a controversy with the Pope, easily defeated Florida Senator Marco Rubio and Texas Senator Ted Cruz, who were fighting for second place and the right to declare themselves the main anti-Trump alternative.
"People (pundits) gave me no chance in South Carolina. Now it looks like a possible win. I would be happy with a one vote victory! (HOPE)," Trump tweeted shortly before the television networks declared him the winner.
It was Trump's second victory in a row, after New Hampshire, an outcome that frightens establishment Republicans but thrills the "throw-the-bums-out" conservative base of the party that has long been fed up with Washington.
A poor showing for former Florida Governor Jeb Bush, who was running in a distant fourth place, could mark the end of the Bush campaign and an end to his dreams of becoming a third Bush president after his father and brother.
After South Carolina, the Republican presidential campaign is about to rapidly pick up steam in March when dozens of states hold nominating contests.
Another candidate, Ohio Governor John Kasich, is concentrating on midwestern and northern states in the state-by-state contest to pick nominees for the November election. Clinton's victory in the Nevada Democratic caucuses could help calm Democratic Party worries about the strength of her campaign.
Her win denied Sanders the breakthrough win he sought in a state with a heavy minority population, but his ability to close a one-time double-digit polling lead for Clinton suggested the Democratic nominating race would be long and hard fought.
With 84 per cent of precincts reporting, Clinton was leading with 52.4 per cent of the vote to Sanders' 47.5 per cent. Vote counting was delayed in Nevada by heavy turnout.
Clinton's victory buoyed worried supporters and gave her fresh momentum as she heads into the next contest in South Carolina on February 28, where polls show her with a double-digit lead largely as a result of heavy support from black voters. "Some may have doubted us, but we never doubted each other," she told cheering supporters at a victory rally in Las Vegas. "This is your campaign."