LAS VEGAS — The top three Republican presidential candidates made a late and vigorous push for support across Nevada as voters headed to caucus locations Tuesday evening in a contest expected to be dominated by Donald Trump.

The billionaire mogul has led every recent public poll by double digits. Enormous crowds have packed his rallies, including one Monday night in Las Vegas that drew an estimated 8,000 people. Trump’s nationalist call to deport illegal immigrants and wall them off has resonated with Nevada’s working-class whites resentful of the booming Latino population.

But a Trump win is no done deal. The state’s caucuses are peculiar and unpredictable –and Sens. Ted Cruz (Texas) and Marco Rubio (Florida) were laboring to spring a surprise on the businessman.

Cruz was hoping to hold three rallies across the state Tuesday before attending a caucus site with his wife, Heidi, in Sparks, a suburb of Reno. Rubio held a morning rally in the Las Vegas area before jetting on to afternoon and evening events in Minnesota and Michigan.

Still, Nevada appeared to b Trump’s to lose.

“You’ve got to vote tomorrow,” he told his Monday night crowd. “You’ve got to vote, vote, vote! . . . We have a big lead, and we don’t want to blow it.”

Unlike in New Hampshire and South Carolina, which had primaries, voters in Nevada had only a four-hour window – from 5 to 9 p.m. – to caucus at select locations. And unlike in Iowa, which held the first caucuses Feb. 1, there is no time-honored tradition of caucusing here.

In 2012, when Mitt Romney won the Nevada caucuses with 50 percent, just 32,894 Republicans participated – roughly 8 percent of the GOP electorate.

Trump made light of Nevada’s arcane voting rules. “Forget the word ‘caucus,’ ” he said at the rally. “Just go out and vote, okay?” He later said: “What the hell is caucus? Nobody even knows what it means.”

Cruz and Rubio were both eager to claim momentum heading into next week’s delegate bonanza known as Super Tuesday. If the two senators can mobilize their supporters – just 20,000 voters could be enough for a landslide, operatives here say – then a win is within reach.

Both campaigns have carefully tailored strategies to exploit what they see as Trump’s weak state-level organization.

Rubio was targeting Nevada’s well-organized Mormon community, which propelled Romney to victory, as well as seniors who populate the many retirement communities around Las Vegas. He also was playing up his local roots. He lived briefly as a child in Las Vegas, where his father tended bar at a casino and his mother cleaned rooms at a hotel.

Cruz, meanwhile, is trying to unite evangelical Christians as well as the self-described liberty voters and constitutional conservatives