Hillary Clinton is the projected winner of the Democratic caucuses in Nevada.

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Early returns show the former first lady gaining roughly half the vote, with Obama at about 45 percent and John Edwards placing a distant third.

Mitt Romney won the Republican side of the competition, while John McCain and Mike Huckabee dueled in a hard-fought South Carolina primary.

The GOP campaign doubleheader is likely to winnow the crowded field of White House rivals.

In a statement released while he flew to Florida, site of the Jan. 29 primary, Romney said Nevada Republicans had cast their votes for change. "With a career spent turning around businesses, creating jobs and imposing fiscal discipline, I am ready to get my hands on Washington and turn it inside out," it said.

Romney's western victory marked a second straight success for the former Massachusetts governor, coming quickly after a first-place finish in the Michigan primary revived a faltering campaign.

Nevada Republicans said the economy and illegal immigration were their top concerns, according to preliminary results from surveys of voters entering their caucuses. Romney led among voters who cited both issues.

Mormons gave Romney about half his votes. He is hoping to become the first member of his faith to win the White House. Alone among the Republican contenders, Rep. Ron Paul of Texas aired television ads in Nevada.

The first scattered returns showed Romney with more than 40 percent of the vote. Paul, McCain and former Tennessee Sen. Fred Thompson were tightly bunched, far behind the leader.

Nevada offered more delegates - 31 versus 24 - but far less appeal to the Republican candidates than South Carolina, a primary that has gone to the party's eventual nominee every four years since 1980.

That made it a magnet for former Tennessee Sen. Fred Thompson, who staked his candidacy on a strong showing, as well as for Romney, McCain, the Arizona senator; and Huckabee, the former governor of Arkansas.

McCain, a former Vietnam prisoner of war, appealed to a large population of military veterans in South Carolina, and stressed his determination to rein in federal spending as he worked to avenge a bitter defeat in the 2000 primary.

Huckabee reached out to evangelical Christian voters, hoping to rebound from a string of disappointing showings since his victory in the Jan. 3 Iowa caucuses.

Romney campaigned on a pledge to help restore the state's economy, much as he did in winning Michigan.

Obama and Clinton both ran all-out in Nevada, even though only 25 delegates are at stake.

Obama won the backing of an influential Culinary Workers Union. That, in turn, led to an unsuccessful lawsuit by some of Clinton's supporters who hoped to ban specially arranged caucuses along the Las Vegas Strip that could draw thousands of unionized casino and hotel workers.

Obama, hoping to become the first black president, spent nearly $1 million in television commercials. Clinton, campaigning to become the country's first woman chief executive, ran nearly $700,000 worth of commercials, and a union group backed her with nearly $100,000 spent on an independent ad campaign.

Former President Bill Clinton was a constant presence, as well, in a state he carried twice on his own in 1992 and 1996.

Remarkably, neither Obama nor Clinton has aired a television commercial criticizing the other, and both of the rivals stepped back earlier in the week from a controversy over race. But that didn't prevent almost constant sniping between the two camps, each pointing out alleged inconsistencies in the other's record.