Next key tests in White House race on Saturday
Democratic presidential candidate Hillary Clinton speaks during a televised town hall meeting with Senator Bernie Sanders at the Cleveland Clinic Lou Ruvo Center for Brain Health in Las Vegas on February 18, 2016 (AFP Photo/John Gurzinski)

White House hopefuls face their third test Saturday when Republicans face off in South Carolina, with Donald Trump enjoying a commanding lead, and Democrats do battle in Nevada, where Hillary Clinton is seeking to bounce back.

As the race moves on, the two parties are on separate battlefields. In South Carolina, Republican voters will cast ballots in a primary, while in Nevada, Democrats will caucus -- grouping themselves together by candidate to voice their support.

Trump is looking for a big symbolic win ahead of "Super Tuesday" -- March 1, when about a dozen states will go to the polls, with a quarter of the nominating delegates up for grabs.

The 69-year-old billionaire finished second to Senator Ted Cruz in Iowa on February 1, before bouncing back in New Hampshire with a big win a week later.

For now, he has 17 delegates, and Cruz has 11. A candidate needs 1,237 to win the right to run in the November 8 presidential election.

Trump -- the onetime reality TV star who has upended the traditional political landscape with his brash style and controversial comments on everything from Muslim immigrants to waterboarding -- has his eye on a particular date: March 15.

After that day, many of the Republican primaries will be winner-takes-all in terms of delegates. If his five rivals are still in the race at that point, they will be splitting the anti-Trump vote -- which mathematically could assure him of the nomination.

On the eve of the vote in South Carolina, Trump was leading in the polls, with about 28 percent of likely Republicans voters backing him, according to an NBC-Wall Street Journal poll released Friday.

The ultra-conservative Cruz follows with 23 percent. Trailing are Senator Marco Rubio at 15 percent and former Florida governor Jeb Bush at 13 percent. The poll has a margin of error of 3.6 percentage points.

The past week on the campaign trail has been a nasty one for Trump and Cruz.

The real estate tycoon repeatedly called the Texas senator a liar, and his attorneys sent Cruz a cease and desist letter over an ad airing in South Carolina that uses a 1999 interview in which Trump said he was "very pro-choice" on abortion rights.

Trump has since changed his stance on the sensitive issue.

"He has a problem with the truth," Trump said Thursday night in a town hall meeting on CNN.

- Clinton bets on immigration -

The backdrop for the Democrats' weekend contest is a bit different -- they have headed to Nevada, land of the desert sun, for Saturday's caucuses.

The key issue at play is the minority vote: blacks, Hispanics and Asian Americans make up roughly half of the state's population.

Clinton, who only won by a hair in Iowa and lost big to rival Bernie Sanders in New Hampshire, is counting on a major Hispanic voter turnout, especially among the hotel and casino employees in Las Vegas.

Since Wednesday, the 68-year-old former secretary of state has visited staff at Caesars Palace -- where she is staying -- the MGM Grand and the Paris casinos, in order to persuade them to join her camp.

The workers, who are generally not wealthy and very unionized, can "caucus" right at their places of employment.

Clinton -- who is seeking to be America's first female president -- has presented herself as the natural ally of Latino families on the issue of immigration, promising a quick path to citizenship for those in the country illegally if she is elected.

The former first lady has relentlessly attacked the 74-year-old Sanders, a self-described democratic socialist senator from Vermont, for voting against immigration reform in 2007.

"If the past is any indication of what the future holds, Senator Sanders will continue to let us down and Hillary will be there fighting for immigrants and the Latino community," Housing Secretary Julian Castro, a possible vice presidential pick, told journalists Thursday.

Sanders has defended himself by saying the 2007 law did not do enough to protect seasonal workers, and that he voted in 2013 for an immigration reform bill, which never came to fruition due to Republican opposition in the House.

"As president, I will do everything that I can to pass immigration reform and a path toward citizenship for those who today are undocumented," he said Thursday on MSNBC.

His supporters are convinced that young minority voters will back him, by the same margin as whites did in the first two nominating contests in Iowa and New Hampshire.

"Of course a lot of our community members are like, 'We are not going to vote for Trump, I must go for a Democrat and the only Democrat we know is Hillary Clinton'," Erika Andiola, a Sanders spokeswoman, told AFP in Las Vegas.

"But now because of the momentum that Bernie has created with the win in New Hampshire and the tie in Iowa, we have been able to have the platform to speak to a broader audience, including the Latino community."