Fresh from the first major victory of his campaign, Republican presidential candidate Mitt Romney arrives in Nevada today to begin the closing arguments on what has been the most extensive effort by a Republican candidate in the Silver State.

Although the former Massachusetts governor comes to the state with the most organized operation of the field, a couple of "X-factors" remain in Nevada's GOP race: Texas Congressman Ron Paul and the potential for a lackluster turnout.

"This has been and should be a Romney state, given his attention and the operation he has built here," said Republican strategist Greg Ferraro of Reno. "But I can't assess Ron Paul. The populist message he's using, I can't tell what kind of traction that has. He is the X-factor."

Although his organizational efforts haven't been as extensive in Nevada, Paul has spent heavily on radio advertising and phone banking here. He also has a devoted contingent of volunteer supporters who have spent large sums on his behalf.

But the most recent poll of likely Republican caucus-goers in Nevada doesn't place Paul in the top five.

No consistent GOP frontrunner has emerged in Nevada since polling began. The lead has traded among Romney, U.S. Sen. John McCain, former New York Mayor Rudy Giuliani and former U.S. Sen. Fred Thompson.

That trend mirrors the Republicans' national struggle to settle on a frontrunner, University of Nevada, Reno political scientist Eric Herzik said.

It's unclear whether Nevada's caucuses on Saturday will help establish a national favorite.

Unlike the Democrats, who made Nevada a cog in their early state strategies, the GOP field mostly has stepped over Nevada. Several forces have aligned to make Nevada the forgotten son of the Republican nominating process.

South Carolina has become an institutional early test for the GOP candidates, having the first say on who is popular in the ever-important South. The Palmetto State's Republican Primary is the same day as the Nevada Caucus.

Nevada Republicans also decided late to move the caucus into the early window, and, as opposed to the Democrats, it was a local rather than a national decision.

But more importantly, not all Republicans are running an early state strategy.

Giuliani has focused his efforts on Florida as his first win to propel him into the Feb. 5 super primary, when 22 states vote or caucus.

Former Arkansas Gov. Mike Huckabee, who has established a strong appeal among evangelical voters and who had slim resources until he caught on in Iowa, never campaigned here.

Paul and California Congressman Duncan Hunter have visited the state often, trying to appeal to what they see as sympathetic constituencies. In Paul's case, that constituency is voters with a libertarian bent. In Hunter's case, it's voters with strong feelings against illegal immigration.

"This election really exposes the divisions in the Republican Party," Herzik said. "You've got the social conservatives, the limited-government conservatives and the traditional Buick-driving, big-business conservatives.

"Nobody in the Republican field right now can cross over into these camps."

Because Nevada hasn't been a major player in the Republican nominating season, the results Saturday won't influence the national dynamic too much, Herzik said.

But Ferraro said Nevada's position as an early test in the West shouldn't be overlooked.

"Winning Nevada would show viability and win-ability in the West," he said. "I do think that is important."

Nevada could be the most important test for Romney, who has built his strategy on early state wins. So far, he has lost the two states that historically have been most important: Iowa and New Hampshire.

His highest profile victory was this week in Michigan, where he was bolstered by voters who remembered his father, George, a popular past governor. He also won Wyoming.

"Gov. Romney had a great night last night," his spokeswoman Sarah Pompeii said. "What it shows is Gov. Romney's optimism triumphs over Washington insider pessimism."