With support from a broad cross-section of Republicans, Romney won by a big double-digit margin over former U.S. House Speaker Newt Gingrich, Representative Ron Paul and former Senator Rick Santorum.
The first results indicated that the former Massachusetts governor was securing nearly 60 per cent of the vote, an increase on his victory four years ago when he took 51 per cent.
Nevada uses a caucus system, with registered Republicans attending party precinct meetings in schools and public halls across the state.
The final caucus was due to open after sundown in Las Vegas, scheduled for observant Jews who could not attend a meeting during the Sabbath.
Newt Gingrich, the former House speaker, and Ron Paul, the Texas congressman, were battling it out for second place, with Rick Santorum, the ex-Pennsylvania senator, trailing in fourth, according to The Telegraph.
The victory was Romney’s second in a row and his third in the first five contests in the state-by-state battle to find a Republican challenger to President Barack Obama in November’s general election.
Mr Romney left Nevada to campaign on Saturday in Colorado, where Republicans will cast their ballots on Tuesday. He is scheduled to return to Las Vegas for a caucus night party for supporters in a casino ballroom later in the day.
Mr Gingrich held a news conference after the results to head off speculation that he might put an early end to his campaign, Reuters reports.
The former House speaker sought to dispel rumors that he would be dropping out of the race.
“Every primary day or caucus day,” a defiant Gingrich declared, “the Romney headquarters in Boston sends out the rumor that they believe I will withdraw, which is of course their greatest fantasy.”
“I’m not going to withdraw,” Gingrich told reporters, repeating his frequent vow to continue all the way to the Republican nominating convention in Florida in August. “I’m actually pretty happy with where we are.”
Gingrich spoke for 25 minutes or so, gleefully pushing back on questions from the press. In the span of three minutes he decried the rise of negative ads, marveled at their effectiveness, and pledged to start bringing knives to the knife fight, only to turn around and proclaim: “I think we are going to make a whole series of positive speeches.”
Of Romney, meanwhile, Gingrich said: “I had never before seen a person who I thought was a serious candidate for president be that fundamentally dishonest.”
“Our commitment is to seek to find a series of victories which by the end of the Texas primary will leave us about at parity with Gov. Romney,” Gingrich said. “And from that point forward, to see if we can actually win the nomination.”
“I am a candidate for president of the United States. I will be a candidate for president of the United States,” he said. “We will go to Tampa.”
Santorum, who finished a distant fourth in Nevada, skipped the state entirely. He said the race would begin to shift as it moved past the first five states, where Romney had an organizational advantage.
“We think this is an opportunity for us to begin to turn this race,” he told CNN. “The more this race goes on, the more people see we present the best chance to win this.”
The month of February, which brings with it a slate of primaries and caucuses that favor either Romney or Rep. Ron Paul (R-Texas), promises to be brutal for Gingrich. His campaign is reportedly low on cash.
According to The Huff Post, he has no formal infrastructure in place in most states and didn’t even make it on Virginia’s ballot. Pressed on all these points, however, his responses drifted between insolence and confusion.
Romney, a former Massachusetts governor, took control of the Nevada contest early after recapturing his front-runner status with a convincing win over Gingrich in Florida last Tuesday.
Entrance polls in Nevada showed that was a persuasive argument, with the economy ranking as the top issue and Romney winning nearly two-thirds of the voters who listed it as their biggest concern.
“America needs a president who can fix the economy because he understands the economy, and I do and I will,” Romney told cheering supporters at a Las Vegas casino hotel, aiming his criticism at Obama and ignoring his Republican rivals.
Romney hopes Nevada will kick off a February winning streak that could position him for a knockout blow to Gingrich during the 10 “Super Tuesday” contests on March 6 – or sooner.