Democrat Hillary Clinton and Republican Mitt Romney were projected to win Nevada's presidential nominating contests on Saturday and voters in South Carolina cast ballots as an unpredictable White House race moved to the South and West.
Major networks projected the Nevada victory for the New York senator, giving the former first lady who would be the first woman president added momentum going into the multiple contests that lie ahead in the nominating race for the U.S. presidential election in November.
Romney's convincing victory in Nevada followed his breakthrough win in Michigan last week after a series of disappointing second-place finishes for the former Massachusetts governor.
Among Democrats in Nevada, polls had shown Barack Obama, an Illinois senator, and Clinton, wife of former President Bill Clinton, in a tight duel after splitting the first two of the state-by-state contests.
In South Carolina, Republicans John McCain and Mike Huckabee fought for the lead in a race focused on the economy, with Romney and Fred Thompson hoping to shove their way to the top in a state where Republicans have a history as kingmakers.
Since 1980, the Republican winner in the South Carolina primary election has gone on to capture the party's presidential nomination.
Cold rain fell across the state and snow was predicted in the north. Voting ends in South Carolina at 7 p.m. EST (midnight GMT), with results expected soon afterward.
"Our voters are committed," Huckabee, a former Arkansas governor, said as he huddled under an umbrella to shake hands with voters in suburban Columbia. "We'll find out if they're committed enough to brave the elements."
The economy has taken center stage in the campaign amid worries about a possible recession taking hold in the United States before the presidential election in November.
(Additional reporting by Jane Sutton and Steve Holland in South Carolina, Jeff Mason in Nevada; Editing by Lori Santos)