Washington (CNN) -- As Mitt Romney leaves Las Vegas, he hopes he hit the jackpot.
Following an hour and a half hour meeting Tuesday afternoon with Nevada billionaire Sheldon Adelson and a few aides, the presumptive Republican nominee was assured the casino magnate was fully supportive of him.
Adelson, who Forbes magazine estimates is worth $24.9 billion and is ranked as the eighth-richest man in America, was largely responsible, along with his wife, Miriam, for keeping Newt Gingrich's presidential bid alive by giving $20 million to the super PAC backing the ex-House speaker's candidacy, Winning Our Future.
Now with Gingrich out of the race, political analysts are looking to see when Adelson will put his next big bet down -- this one on Romney.
Adelson did not attend a high-profile Romney fund-raiser Tuesday night at the Trump International Hotel but later went to a smaller dessert donor reception at a private residence with Romney and Gingrich, a source familiar with the event told CNN.
The key motivation for Adelson this campaign is preventing the re-election of President Barack Obama, those knowledgeable about the billionaire's thinking have said. He reportedly sees Republicans as stronger proponents for Israel's safety, which friends have said trumps all other concerns for him and was a key factor in his support for Gingrich, a longtime friend of his.
"He is very focused on defeating Barack Obama," one friend told CNN. "He is going to be the Republican Party's 800-pound gorilla in defeating Barack Obama.'
During the GOP primaries, Adelson told associates that he would back whoever won the nomination and that he now fully supports Romney, sources have told CNN. About a dozen financial backers of Romney and other major Republican donors met with Adelson in Las Vegas while they were in town for a meeting of the Republican Jewish Coalition to convince him to "come on board" with respect to supporting Romney. He indicated to them, according to one of the participants, "it is just a matter of time."
However, the question is when and how much.
As of April 30, he had not given to the pro-Romney super PAC, Restore Our Future.
When Las Vegas columnist Jon Ralston asked Adelson in late April whether he was going to donate to Restore Our Future, he said, "I'm not going to tell you. ... You'll find out when it's reported."
Adelson said at the time he wanted to become less visible in the political world and that references to him being a mogul when his donations were reported were "not helpful to that person."
Asked if he was going to give to the Republican super PAC American Crossroads or its nonprofit affiliate Crossroads GPS, he initially would not answer. Later, he said to Ralston, "I'm going to give one more small donation -- you might not think it's that small -- to a super PAC and then if I give it will be to a C4," referring to 501(c)(4) nonprofit groups, such as Crossroads GPS, which are not required to disclose their donors.
While he has been complimentary of Romney in some private sessions, according to one source familiar with the matter, he also has publicly criticized him for lacking decisiveness -- an attribute he said Gingrich demonstrated.
"He's not the bold decision-maker like Newt Gingrich is. He doesn't want to -- every time I talk to him, he says, 'Well, let me think about it,' " Adelson told JewishJournal.com at the end of March.
Adelson has been a prolific donor to Republican causes. Earlier this year, he and his wife each donated $2.5 million to the Congressional Leadership Fund, a group dedicated to keeping the Republican majority in the House of Representatives. The Adelsons hosted a fund-raiser in April for House Speaker John Boehner's re-election campaign.
According to the Center for Responsive Politics, a nonpartisan group that tracks the role of money in politics, Sheldon and Miriam Adelson rank as the top individuals funding outside spending groups this election cycle.
In February, when Gingrich still seemed to have a shot at the Republican nomination, Adelson told Forbes magazine he might give as much as $100 million to support the former House speaker. What is unclear is whether he will follow through giving that amount to others.
In that interview, he defended his donations and said he had nothing for which to apologize.
"I'm against very wealthy people attempting to influence elections," he said. "But as long as it's doable, I'm going to do it. Because I know that guys like (George) Soros have been doing it for years, if not decades. And they stay below the radar by creating a network of corporations to funnel their money. I have my own philosophy, and I'm not ashamed of it. I gave the money because there is no other legal way to do it. I don't want to go through 10 different corporations to hide my name. I'm proud of what I do, and I'm not looking to escape recognition."
The Adelsons came under some criticism from Republicans for their support of the super PAC backing Gingrich, especially when it aired bitter ads in January questioning Romney's record at Bain Capital and also when it became clear that Gingrich's candidacy had stalled. One friend said Adelson saw his support as fulfilling his commitment to Gingrich.
Adelson reacted to the critics in the Forbes interview: "Those people are either jealous or professional critics."
He added: "They like to trash other people. It's unfair that I've been treated unfair -- but it doesn't stop me."
CNN political producer Rachel Streitfeld contributed to this report.