Everyone can now start using the F-word to describe Donald Trump. And feel safer using it to describe Hillary Clinton once again.


Voters cast ballots Saturday in two races that could shape the U.S. presidential primaries leading into Super Tuesday — Trump won the Republican primary in South Carolina, and Clinton captured the Democratic caucuses in Nevada.

Trump won a victory that made him the clear Republican frontrunner, by historical standards: Nobody in the modern era has won New Hampshire and South Carolina, then gone on to lose the nomination.

There was only one sour note for him.

Trump alluded to it dismissively in his victory speech. But the collapse of the also-rans in the field increased the likelihood of fourth- and fifth-place candidates dropping out and rallying behind the more like-minded Marco Rubio.

That was underscored immediately as Jeb Bush exited the race. His announcement drew loud cheers at a Rubio rally. Fans of the Florida senator immediately speculated that supporters and donors of the former Florida governor would inevitably start gravitating their way — toward the campaign of Bush's old friend and protege.

Rubio saluted the life and work of his old ally. He then quickly made a pitch for Bush's voters.

"After tonight this has become a three-person race," Rubio told a jubilant crowd, which celebrated the senator's second-place finish.

"And we will win the nomination... Now, practically speaking, we're down to three."

Trump took 33 per cent of votes, Rubio took 22 per cent, finishing just ahead of firebrand conservative Ted Cruz and miles ahead of the rest of the pack. Bush and Ohio Gov. John Kasich each took eight per cent, while neurosurgeon Ben Carson took seven per cent.

It was a quick, anti-climactic end for Bush. He'd roared into the campaign as a presumed favourite with money, the party establishment, and the Bush dynasty at his back — but his juggernaut failed to launch.

Grassroots conservatives were unpersuaded by his quite conservative gubernatorial track-record, and remained unmoved when he made a nostalgia play late in the campaign by trotting out famous family members.

While Bush is gone, other also-rans have chosen to fight on for now. The race is now on to scoop up delegates on March 1. A dozen states vote on Super Tuesday, delivering a motherlode of delegates compared to the few handed out so far.

As for Clinton, Saturday's results were a potential campaign-saver.

She staved off what could have been a ground-shifting loss to Bernie Sanders, the socialist senator who has put up a surprisingly strong challenge and threatens to eclipse her.

The former secretary of state clung to a four-percentage-point lead in Nevada — not nearly the advantage she once had in polls, but perhaps enough to quash talk of a campaign death-spiral.

"Some may have doubted us, but we never doubted each other," Clinton told supporters.

She listed parts of her campaign platform, arguing that it would achieve more for regular Americans than the angry anti-business rhetoric of her opponent — whom she describes as a single-issue candidate: "Americans are right to be angry, but we're also hungry for real solutions."

Trump expressed awareness in his last campaign rally that winning isn't the only thing that matters. In his latest campaign speech, he urged every supporter to get out and vote: "The more we can win by, the bigger the mandate, the better it is."

But he was dismissing that same logic in his victory speech Saturday. He poked fun at pundits who speculated the field might now narrow to his disadvantage.

In an early taste of the next phase of the race, Rubio criticized some recent language from Trump.

The New York billionaire appeared to have mastered one of the less-charming traditions of campaigning in South Carolina: racial dog-whistling. Trump's whistles were at a low-enough frequency for any human to comprehend.

Trump tweeted an observation Saturday that perhaps the reason President Barack Obama isn't attending the funeral of Supreme Court Justice Antonin Scalia is because it's not being held in a Muslim mosque.

This was after he delivered a speech the previous night where he recited an urban legend: about a U.S. general scaring off a Muslim insurgency by killing 49 Muslims with bullets dipped in pig's blood — then telling the 50th to warn his friends.

The story appears to be, at best, a drastically embellished combination of two other tales from the early 20th century — and at worst a complete fabrication, the equivalent of an Internet chain letter being aired from the podium of a U.S. presidential campaign.

Trump also defended torture in his final campaign speech Friday.

He called waterboarding "minor, minor, minor" torture — and when describing how he felt about the now-abandoned tactic he said, "I feel great about it."

Rubio reacted to the pig's-blood story.

"I'm sure people were offended. I hope people were offended by that. That's not what the United States is about. It's doubtful whether that even happened," he said. "We're in a very weird year here... People are saying whatever they want in politics today and there seems to be no accountability."

He said the presidency is a serious job and it's time to start talking about serious things — not the "circus."

Among Democrats, Clinton retains a big lead with African-American voters and is expected to win next week in South Carolina and other southeastern states on March 1.

But until recently she also had a huge lead in Nevada, which has a large Latino population — and that essentially disappeared.