LAS VEGAS, Nev. -- In a whirlwind half-day visit to Sin City, Mitt Romney is enlisting a powerful new financial backer, rallying the troops with the state's governor and is set to collect millions at a high-dollar fundraiser with the ever-controversial Donald Trump, all before the sun sets in the desert tonight.

No sooner had Romney's campaign parked the chartered 737 plane (right next to Donald Trump's black and gold emblazoned jet), the candidate was off to meet with billionaire casino magnate Sheldon Adelson, who almost singlehandedly kept Newt Gingrich's campaign afloat with millions of dollars in donations to Gingrich's super PAC, but signaled months ago he would support the Republican nominee.

Aides said the meeting lasted nearly an hour at the Venetian Las Vegas Casino, Hotel and Resort, but there was no word of a formal endorsement or gift to the pro-Romney super PAC.

Romney next visted a Somers Furniture warehouse, but not for a new ottoman. The former Massachusetts governor campaigned for the first time with Nevada Governor Brian Sandoval, a rising star in the Republican party who originally backed Texas Governor Rick Perry early in the primary campaign.

Romney took aim at President Barack Obama's 2009 comments not to "blow a bunch of cash in Vegas," by pledging his love for the city, which helped deliver a major caucus win for the all-but-certain Republican nominee back in February.

"I'm counting on you guys to go out and make sure that you elect a president who tells people to come to Las Vegas, not to stay away from Las Vegas. Who gets us on the track to have a strong and vibrant economy again," Romney said.

As Romney continued to attack the president as "hostile" to business, he veered into new territory, passing along the story of a restaurant owner he met with in a closed-door roundtable who suggested adding a new provision to the constitutional requirements of the presidency: time in business.

"I’d like to have a provision in the Constitution that in addition to the age of the president and the citizenship of the president and the birthplace of the president being set by the Constitution, I’d like it also to say that the president has to spend at least three years working in business before he could become President of the United States," Romney quoted the restauranteur as saying. "You see then he or she would understand that the policies they’re putting in place have to encourage small business, make it easier for business to grow."

And perhaps no man is more embroiled over the constitutional requirements of the presidency than Romney's host at his final Vegas event of the day, Donald Trump, who today doubled-down on his controversial beliefs that President Obama's birth certificate may be fraudulent, telling CNN that "a lot of people don't agree with that birth certificate," a charge host Wolf Blitzer labeled "ridiculous."

Trump hosted the fundraiser for Romney tonight at the Trump International Hotel just off the Las Vegas strip with a top asking price of $50,000. Trump spokesman Michael Cohen said the event tonight could raise "millions" for Romney campaign's victory fund.

Among the guests was Newt Gingrich who said, “We believe this is an American-born, job-killing president.”

Answering a question about Trump, he continued: “Others believe he was born elsewhere and kills jobs. But Obama is a jobs-killing president. He was born in Hawaii. That doesn’t affect that he is killing jobs.”

By NBC's Michael Isikoff

Sheldon Adelson, the billionaire casino mogul bankrolling Newt Gingrich’s super PAC isn’t trying to “buy” a presidency, his top political consultant tells NBC News.  He’s just following in the footsteps of another powerful business tycoon, Joseph Kennedy, father of President John F. Kennedy. 

“I don’t think it’s buying a presidency any more than it was when Joe Kennedy helped his son,” Sig Rogich, a veteran Republican operative who serves as Adelson’s government affairs consultant, said in an interview about the massive donations that the casino mogul has made to Gingrich’s super PAC.

Adelson, 78, who has a personal fortune estimated at $21 billion, “plays to win” and “puts his money where his mouth is,” Rogich added. 

In the last three weeks, Adelson and his Israeli-born wife Miriam have pumped $10 million into the Winning Our Future Super PAC. Those donations provided a critical cash infusion that helped revive Gingrich’s candidacy, bankrolling attack ads against Mitt Romney in South Carolina and now Florida.  They’ve also made the Adelsons the largest known donors so far in a presidential race awash with money under new rules allowing unlimited donations to so-called super PACs. 

But the contributions have also raised new questions about Adelson’s outside role in influencing the campaign.  Those questions could intensify as a result of potentially provocative comments he has made about Israel uncovered by NBC News. 

Scott Audette / Reuters

Republican presidential candidate former Speaker of the House Newt Gingrich makes a point during the Republican presidential candidates debate in Jacksonville, Florida January 26, 2012.

Adelson owns a newspaper in Israel, 'Israel HaYom,' that backs conservative Prime Minister Benjamin Netanyahu, and adamantly opposes any peace settlement with the Palestinians.

But while Adelson and Gingrich have bonded on the issue of a hawkish Mideast policy, especially over the threat of a nuclear Iran, some of the casino mogul’s comments could prove embarrassing.

In a talk to an Israeli group in July, 2010, Adelson said he wished he had served in the Israeli Army rather than the U.S. military—and that he hoped his young son would come back to Israel and “be a sniper for the IDF,” a reference to the Israel Defense Forces. (YouTube video of speech)

“I am not Israeli. The uniform that I wore in the military, unfortunately, was not an Israeli uniform.  It was an American uniform, although my wife was in the IDF and one of my daughters was in the IDF ... our two little boys, one of whom will be bar mitzvahed tomorrow, hopefully he’ll come back-- his hobby is shooting -- and he’ll come back and be a sniper for the IDF,” Adelson said at the event.

“All we care about is being good Zionists, being good citizens of Israel, because even though I am not Israeli born, Israel is in my heart,” he said toward the end of his talk.  

Asked about those comments, Rogich said: “No one could possibly ever think that he is anything but a loyal American.  He’s shown that time and time again.”

Rogich cited major donations that Adelson has made to medical research and other philanthropic causes that were far bigger than his political contributions, he said.

As for Israel, Rogich said: “I think that the fact that he is a Zionist and believes deeply in the preservation of Israel is so commendable.”

Newt Gingrich, who stirred controversy recently by calling the Palestinians "an invented people," appears on the cover of Sheldon Adelson's newspaper, Israel HaYom, blasting the Obama administration for its policies on Iran. "The Obama administration is denying reality," reads the headline in Hebrew. "The refusal to confront evil could cause a second Holocaust."

Gingrich, who stirred controversy recently by calling the Palestinians “an invented people,” appeared on the cover of Adelson’s Israeli newspaper blasting the Obama administration for its policies on Iran.

“The Obama administration is denying reality,” reads the headline in Hebrew. “The refusal to confront evil could cause a second Holocaust.”

When Gingrich was questioned about the money from Adelson this week, he immediately cited the casino mogul’s backing of Israel as a major reason he had received his support.

“Sheldon Adelson is very deeply concerned about the survival of Israel and believes that the Iranians represent a mortal threat to Israel and the United States,” Gingrich said in an interview while on the campaign trail in Florida.  “And he is deeply motivated by the question of having a commander-in-chief strong enough and willing to make sure the Iranians do not get nuclear weapons.”

Asked if he had promised the casino mogul anything in exchange for the money to the super PAC, Gingrich replied: “I promised him that I would seek to defend the United States and the United States allies.”

Adelson’s interests extend beyond Israel.  His personal fortune comes from a casino empire that stretches from the Vegas strip to the gambling havens of Singapore and Macau.  But his business interests have also provoked legal troubles.  

Adelson’s company, the Las Vegas Sands,  disclosed last year that it was being investigated by the U.S. Justice Department and Securities and Exchange Commission over allegations by a former top company executive that Adelson directed him to put a local government official on its payroll in Macau — a potential violation of a U.S. anti-bribery law.  The firm has denied the allegations, saying they come from a lawsuit filed by a disgruntled former employee.

Adelson also earned a reputation in Las Vegas as a fierce foe of labor unions after he bought the legendary Sands Hotel, home base of Frank Sinatra’s Rat Pack, and then blew it up in 1996.

About 1,500 casino workers lost their jobs.  Adelson built a spectacular new hotel in its place, the Venetian, but locked out the state’s powerful Culinary Workers Union, which resulted in street protests and lawsuits.

Union official D. Taylor (sic) said that Adelson’s security officials at the Las Vegas Sands Hotel tried to have the protestors outside his hotel arrested, but Las Vegas police refused.

“He claimed that he owned the sidewalks,” Taylor said.  Georgia Democratic “congressman John Lewis led us on the sidewalks to say that nobody’s going to own the people on the sidewalks,” he added. “Sheldon then appealed the decision of the police not to arrest us all the way to the Supreme Court.”

Taylor said Adelson lost that battle — the courts upheld a finding of anti-labor practices against his company — but now the casino mogul thinks he can purchase a presidency.

“I think it’s very scary that any one candidate would be so beholden to one persona, a billionaire, who obviously has a very specific agenda that he wants to achieve,” said Taylor.

But Rogich, Adelson’s consultant, said that agenda consists of nothing more than trying to elect a good friend who he believes “would be a great president.”

“And that’s what this process is all about — that’s why we call it America,” he said. “You have the right to spend your money how you’d like to spend it.”