Candidates in the 2016 White House race face key, early-state voting on Saturday -- Democrats in the Nevada caucus and Republicans in the South Carolina primary.

The Democratic Caucus between front-ruer Hillary Clinton and surging Vermont Sen. Beie Sanders appears too close to call, with the polls having opened at 11 a.m. local time.

Clinton has until recent weeks held a double-digit lead in Nevada, after narrowly wiing the Iowa Democratic caucus, then losing to Sanders in the party’s New Hampshire primary.

The former first lady and secretary of state leads Sanders roughly 49 to 46, according to the latest RealClearPoltics.com poll average.

Her campaign had hoped to stop Sanders as the primaries move into the Southe and Weste states, in which Clinton has strong support from minority voters and unions.

In South Carolina, national front-ruer Donald Trump holds onto a double-digit lead with GOP Sens. Ted Cruz, Texas, and Marco Rubio, Florida, deadlocked for second place with roughly 19 percent of the vote, compared to 32 percent for Trump, the billionaire businessman.

Still, many voters said before the polls opened that they were still undecided.

Former Florida Republican Gov. Jeb Bush is close behind the lead pack. He is hoping to do well in the largely conservative state, whose electorate includes lots of military and ex-military voters.

Bush said Saturday that he's "excited where we stand" and that he going to "work hard for the day" and await results after the polls close at 7 p.m. local time.

He also remarked that a lot of people claiming they're undecided this late is “interesting.”

The former Florida goveor entered the 2016 presidential race as an early favorite.

But Bush may need a third-place finish, if not better, in South Carolina to compete in the GOP primary next week in Nevada, then in the large number of states voting on March 1.

A Trump victory could foreshadow strong showings in the Southe states that vote on March 1 -- when he could pile up the delegates that determine the nominee.

Cruz hopes his get-out-the-vote operation and lots of volunteers can help overtake Trump in South Carolina.

The Associated Press contributed to this report.