LAS VEGAS, Nevada — Real estate tycoon and reality TV star Donald Trump threw his weight behind Republican frontrunner Mitt Romney on Thursday, in a glitzy boost for the former Massachusetts governor's White House hopes.

In typical Trump style, he had kept poll-watchers guessing until the last moment; as late as Wednesday evening a senior Gingrich official claimed Trump would endorse his presidential candidate.

Also in trademark populist fashion, he announced his backing in the lavish surroundings of his vast shiny gold-colored Trump Hotel and Tower in Las Vegas, telling Romney to "go out and get 'em."

"It's my honor, real honor and privilege to endorse Mitt Romney," he said, with the candidate and his wife Ann at his side in the desert gambling center where team Romney was campaigning ahead of Nevada's caucuses on Saturday.

"Mitt is tough, he's smart, he's sharp, he's not going to allow bad things to continue to happen to this country that we all love," Trump added.

"Governor Romney, go out and get 'em, you can do it," he added, before the two multi-millionaires shook hands for the cameras.

Romney drew laughter when he replied: "There are some things that you just can't imagine happening in your life. This is one of them. Being in Donald Trump's hotel and having his endorsement is a delight."

Some observers had thought it more likely that Trump would endorse the less buttoned-down Gingrich to be the Republican nominee to face off against President Barack Obama in the November election.

The significance of Trump's endorsement is unclear. Although he has a populist touch, pollsters suggest that not many voters would change their mind about a candidate because of his backing.

Heather LaMarre, professor of political communications at University of Minnesota, said Trump's endorsement was important, especially if it is followed by other Tea Party favorites like congresswoman Michele Bachmann.

"When you start to get Donald Trump and then Michele Bachmann and then a cascade of these Tea Party types endorsing him, it's going to create a momentum among the base. It is momentum-building," she said.

In Washington, when asked about the Donald's endorsement, Obama's spokesman Jay Carney joked: "I'm not going to comb over that question," in a reference to the real estate tycoon's famous hair style.

He said he had nothing else to add, other than recalling Obama's famous roasting of Trump at the annual White House Correspondent's dinner last year, when he mocked the magnate for questioning if he was born in the United States.

The two main Republican candidates arrived in Las Vegas shortly after Romney soundly defeated Gingrich in Tuesday's Florida primary, re-establishing himself as the frontrunner in the race.

A new poll Thursday gave Romney a clear lead over Gingrich in the western battleground state of Nevada, with 45 percent to the former House speaker's 25 percent.

Gingrich has been endorsed by ex-candidate Herman Cain, and former Alaska governor Sarah Palin had urged Florida voters to back him in order to extend the contest, a sign of his support among the ultra-conservative Tea Party.

However, most of the party's establishment figures -- including Senator John McCain and popular New Jersey Governor Chris Christie -- have backed Romney.

In December, Romney snubbed Trump by declining to participate in a debate to be hosted by the tycoon, although Trump later said he did not resent Romney's decision.