Republican presidential front-runner Donald Trump decisively won the South Carolina primary on Saturday, prompting former Florida Governor Jeb Bush to quit the race, thus trimming the GOP nomination contest to just five contenders.

On the Democratic side of the electoral battle, Hillary Clinton held off a late surge from Bernie Sanders to win the Democratic caucuses in Nevada.

With 47 percent of precincts reporting late on Saturday, Trump had 34.0 percent of the votes in South Carolina, followed by Sen. Ted Cruz and Sen. Marco Rubio, who are tied at 21.6 percent, Newsmax reported.

Bush had 8.2 percent, with Ohio Governor John Kasich at 8.1 percent and retired neurosurgeon Ben Carson at 6.5 percent.

Trump's victory follows a second-place finish in Iowa on Feb. 1 and a massive victory in New Hampshire on Feb. 9.

Trump was the runaway winner throughout South Carolina, with exit polls showing he won most major demographic groups. Even among evangelical Christians, Trump beat Cruz, 31 percent to 27 percent.

The real estate magnate also won the largest share of the vote among those who consider themselves moderates and those who self-identified as somewhat conservative. On the other hand, Cruz beat Trump, 37 percent to 27 percent, among those who said they're very conservative.

Trump easily won the votes of present and past members of the military, a large sector in South Carolina. He also won the largest share of the vote among those 45 years and older and all levels of education.

Experts consider the South Carolina primary results as a preview of the bigger contests in March in other southern states.

Trump won despite sparring with Pope Francis on immigration issues and with Cruz on the latter's alleged lying and campaign dirty tricks.

South Carolina awards 50 delegates and Trump is expected to win a large share of them. More than half of the delegates—29—are awarded to the overall winner. The rest are apportioned based on who wins in each of South Carolina's seven congressional districts.

Significantly, the winner of South Carolina's Republican primary has gone on to become the party's nominee since 1980, with just exception—Newt Gingrich in 2012. But Gingrich lost to eventual Republican nominee Mitt Romney, who subsequently lost to reelectionist Democratic President Barack Obama.

Following the vote, Bush gave an emotional statement, saying, "the presidency is bigger than any one person."

Bush, once the favourite to win the GOP nomination, had hoped for a strong showing in South Carolina, a state his father and brother both won on the way to the White House. His fourth place finish was far from what he expected.

Bush even brought his brother, former President George W. Bush, onto the campaign trail this week in South Carolina to boost his candidacy, but the vote results showed this was not enough to improve his fortunes.

In Nevada, Newsmax said Clinton won 53 percent of the caucus vote to 47 percent for Sanders with about 88 percent of precincts counted as of late Saturday, according to results released by the Nevada Democratic Party.

"Some may have doubted us but we never doubted each other, and this one's for you," Clinton told supporters at Caesars Palace in Las Vegas.

Sanders called Clinton to congratulate her. However, in his concession speech, Sanders said Nevada was just the start of his campaign and that people are beginning to hear his message.

"The American people are catching on that we have a rigged economy," he said to campaign workers and supporters. "It is clear to me that the wind is at our backs. We have the momentum."