Sheldon Adelson and his wife, Miriam, give a news conference at the Marina Bay Sands complex in Singapore in June 2010. (ROSLAN RAHMAN/AFP/GETTY IMAGES)

The way casino magnate Sheldon Adelson remembers it, he and his wife, Miriam, met then-House Speaker Newt Gingrich in 1995 in the majestic Capitol Rotunda as they made their way through the building while lobbying for a bill to move the U.S. Embassy in Israel from Tel Aviv to Jerusalem.

Nearly two decades later, Gingrich, on the campaign trail, has promised that his first executive order as president would be the embassy move, long a priority of ardent Israel supporters such as the Adelsons.

It would also be a sweet jackpot for the Adelsons, who are the biggest patrons of Gingrich’s political career.

Perhaps no other major presidential candidate in recent times has had his fortunes based so squarely on the contributions of a single donor, as Gingrich has on Adelson, who has spent millions in support of Gingrich and his causes over the past five years. In a primary season dominated by the mega-spending of super PACs, Adelson’s efforts on Gingrich’s behalf provide a window into the expanding influence of the super-rich on American politics.

After putting up the seed money and ultimately $7.7 million between 2006 and 2010 for a nonprofit group that served as a precursor to Gingrich’s presidential campaign, Adelson, 78, an irascible Las Vegas billionaire, doubled down this month, giving $5 million to a political action committee run by former close aides to Gingrich.

“My motivation for helping Newt is simple and should not be mistaken for anything other than the fact that my wife Miriam and I hold our friendship with him very dear and are doing what we can as private citizens to support his candidacy,” Adelson, who is listed by Forbes as the eighth-wealthiest American, with a net worth of $21.5 billion, said in a prepared statement e-mailed to The Washington Post. He declined interview requests.

The most recent donation to Winning Our Future, a Gingrich-linked super PAC, fueled Gingrich’s resurgence before Saturday’s primary in South Carolina and bankrolled ads and a half-hour film painting rival Mitt Romney as a job-killing corporate raider. Adelson told associates that he will consider more donations if Gingrich fares well Saturday.

For Gingrich, the check links him even more closely to Adelson (pronounced ADD-el-son), an outspoken businessman known for aggressive tactics. His net worth has increased at least ninefold in the last decade. (The FBI and Securities and Exchange Commission are investigating his company, Las Vegas Sands, in connection with allegations that Adelson ordered an executive to bribe Chinese officials by putting them on the payroll. Adelson and company officials deny the allegations, which they say were first made by a disgruntled former employee.)

Adelson said the check to Gingrich was about fidelity. “Our means of support might be more than others are able to offer,” he said, “but like most Americans, words such as friendship and loyalty still mean something to us.”

Friends said Adelson and Gingrich share views on Israel, labor and free enterprise. In December, when Gingrich was riding atop the national GOP polls, Adelson was delighted.

“He was extremely proud,” Fred Zeidman said last month after he saw Adelson at a board meeting for the U.S. Holocaust Museum, to which the Adelsons are multimillion-dollar donors. “He was very excited about where they were.”

Miriam Adelson was born in Israel, and the couple donate to Jewish causes. They have given more than $100 million to Birthright Israel, a charity that pays for Jewish youths to visit Israel.

When the Adelsons were in Israel in December, to attend a Hanukkah ceremony for the program, Sheldon praised controversial comments made by Gingrich last month on the Jewish Channel, a U.S. cable network.

“Read the history of those who call themselves Palestinians, and you will hear why Gingrich said recently that the Palestinians are an invented people,” Adelson was quoted as saying by the Web site of the Israeli newspaper Haaretz.

Sheldon Adelson credits then-Rep. John Linder (R-Ga.), now retired, with introducing the Adelsons to Gingrich at the Capitol, though Linder does not recall being the matchmaker. The encounter came just before passage of the Jerusalem Embassy Act. Though the act had bipartisan support, presidents Bill Clinton, George W. Bush and Barack Obama have declined to implement it, deeming it an infringement on the president’s sole constitutional authority to conduct foreign affairs.

Adelson has staunchly defended Gingrich to fellow Jews. When Jewish Week wrote a story in May headlined, “Will Gingrich Bomb With Jewish Republicans?” Adelson called up a columnist at the paper to complain. “There is not a better advocate for Israel,” Adelson told the columnist.

If Israel first brought brought them together, the relationship was sealed during a crisis for Adelson, said George Harris, who was a consultant for Adelson at the time and now is co-finance chairman of Gingrich’s campaign.

A few years after the embassy vote, Harris arranged for Adelson to meet with Gingrich when he was traveling to Nevada for a fundraiser.

A poor cab driver’s son born to Ukrainian Jewish immigrants living in Dorchester, Mass., Adelson rose from being a mortgage broker to making hundreds of millions of dollars by selling Comdex, the computer trade show in Las Vegas. He then purchased the old Sands hotel, once the base of Frank Sinatra’s Rat Pack, and demolished it in 1996. He broke ground a year later to replace it with an opulent $1.5 billion resort, the 4,000-room Venetian, now the sixth-largest hotel in the world.

Culinary unions were trying to pressure Adelson into accepting a union shop. Harris remembers union protesters picketing in front of the Venetian’s preview center with signs saying that if Adelson didn’t agree to a contract, “We will wail at your Wailing Wall.”

Harris thought a visit with the House speaker would boost Adelson’s spirits and raise his stature during the labor dispute. After Gingrich attended fundraising events, the Adelsons and Gingrich had dinner, he said.

“From my perspective, it was all about bringing more national clout to Sheldon,” Harris said. “They hit it off. These are two guys who spent the majority of their day trying to think of how to make America great.”

The Venetian opened in 1999 — as a nonunion resort.

Looking to expand his gambling empire, Adelson turned to Asia. The Chinese were looking for a new casino operator for freewheeling Macao, the resurgent former Portuguese colony near Hong Kong that was returned to Chinese control in 1999.

Adelson wanted in, and he was not averse to flexing his political muscle. He later testified in a lawsuit that he called Rep. Tom DeLay (R-Tex.), then House majority leader, in 2001 on behalf of Chinese officials concerned that a House resolution on human rights would hurt Beijing’s chances to host the 2008 Olympics.

DeLay told him the bill had been put on hold — and Adelson led the Chinese to believe he had something to do with it, according to testimony in the lawsuit. “Did the Chinese think that [Adelson] had been helpful in the Olympics?” Las Vegas Sands attorney Rusty Hardin told a jury. “Yeah, I’m sure they did.”

China awarded Adelson a coveted gambling concession. The Sands Macao opened in 2004.

Two years later, as Adelson was building the 3,000-room Venetian Macao, Gingrich traveled to Hong Kong and Singapore. Gingrich wrote in a column for Human Events about visiting with a casino developer whom he did not name.

“One casino developer I spoke to while I was there is building a billion-dollar-plus casino and resort in Macao, China,” Gingrich said. “He summed up one of our core challenges of competing in the global economy: ‘I have done two billion-dollar projects in Las Vegas and China in the last few years. The workmanship in China was better and the 62,000 applicants for jobs were more enthusiastic and better qualified.’ ”

During Gingrich’s visit, Las Vegas Sands was selected over three rivals to develop Singapore’s first casino resort. An official close to Adelson said that to the best of his knowledge, he was not aware of anything Gingrich ever did for Adelson’s casino business.

At the time, Gingrich told the Straits Times in Singapore that he was in Asia to research a novel on World War II.

A spokesman for Adelson said that he was not in Asia at the time.

Regardless, the two men’s ties remained strong. And soon they turned financial.

Adelson wrote a check six months after the trip, supplying the $1 million in seed money for a new nonprofit political organization created by Gingrich called American Solutions for Winning the Future.

It was one of only two checks the group received in 2006. The other was for $35,000.

Adelson’s first $1 million did not last long.

In less than a year, American Solutions had burned through most of the Adelson money, and by late summer he was solicited for more, according to two former employees and spending reports.

Adelson agreed, but only after the group had amped up its own fundraising. Adelson told American Solutions he would do a dollar-for-dollar match for the “527” group, a nonprofit permitted to engage in some political activities. American Solutions ultimately spent $2 for every $3 raised on administration and fundraising, records show.

Several Gingrich employees, who were not authorized to speak publicly, said they were concerned about how Adelson’s money was being spent, particularly for private charter travel that cost from $30,000 to $45,000 a flight.

The employees said that when Gingrich had out-of-town meetings for his for-profit Center for Health Transformation, staff would be asked to find events as well for American Solutions. “American Solutions events were put on the books to have something in the city to pay for airfare,” a former official of the group said.

Over five years, the charter jet travel cost $6.6 million.

“His personal accountant had expressed real concerns,” the former official said. “I don’t think he flew commercial for almost a two-year period. It was a huge drag on American Solutions.”

Gingrich’s campaign spokesman, R.C. Hammond, did not respond to written questions for the story. Hammond, who also was previously spokesman for American Solutions , said the 527 group had heard few complaints about high fundraising costs.

Researcher Lucy Shackelford and research editor Alice Crites contributed to this report.