FORTUNE — The business world knows quite well who Sheldon Adelson is — the eighth richest American who has alternately lost and recouped tens of billions of dollars in the casino business over the last few years. A wider public came to know him when two $5 million checks signed by Adelson bolstered Newt Gingrich’s faltering presidential campaign earlier this year, threatening to upend the Republican primary race. But only one was signed by Sheldon. The other: Miriam.
While she is much less well-known than her husband, Miriam Adelson is not your average billionaire’s wife. Rather, she is an accomplished medical doctor, as well as her husband’s partner in a range of business and philanthropic activities. As the dynamics of the race shift, what has become clear is that this driven and passionate pair is bound to have an influence on the 2012 campaign. On Monday, The Wall Street Journal reported that they were quite possibly preparing to shift their backing to Romney — they seem prepared to support any Republican in their hope of seeing Barack Obama defeated this fall. And Gingrich is in no way the only recipient of their largesse so far — according to the Center for Responsive Politics, the couple ranks second in individual contributions to parties, federal candidates, and PACs in the current election cycle. They also spent $30 million during the 2008 election. Indeed, in an exclusive interview with Fortune, Dr. Adelson emerges as no less accomplished — or powerful — than her larger-than-life spouse.
Israeli-born Miriam Ochshorn, 66, has been married to 78-year old Adelson since 1991, and the couple has four children together. Her parents, Menucha and Simha Farbstein, fled Poland in the run-up to the Holocaust, settling in Haifa. There her father ended up owning a handful of movie theaters, though the family didn’t have a television until Miriam was 16. Her husband comes from equally modest beginnings — the son of a Boston taxi driver, Sheldon Adelson grew up in a one-room tenement in Boston’s Dorchester section.
Dr. Miriam Adelson — known as Miri to her friends — earned a Bachelor of Science in Microbiology and Genetics from the Hebrew University of Jerusalem. During her two years of military service in Israel, she worked in the biological research department, and followed that by earning a medical degree from Tel Aviv University’s Sackler Medical School. She went on to become the chief internist in an emergency room at the Rokach Hospital in Tel Aviv. In 1986, she served as an associate physician at Rockefeller University in New York, where she studied chemical dependency and drug addiction, with a specific focus on the spread of HIV among drug addicts. Her mentor was Mary-Jeanne Kreek, the researcher credited with discovering that methadone was a safe treatment for addicts. The two women have since collaborated on studies of methadone and addiction for the last 25 years.
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Adelson, now 66, says her heart has always remained in Israel, but she got “stuck” in America after meeting Adelson—“the love of [her] life”—on a blind date in 1991. Suddenly extremely wealthy, Dr. Adelson started putting some of that casino lucre to good use. In 1993, she founded a substance abuse center and research clinic at Tel Aviv’s Sourasky Medical Center, with a mission that supported the then-controversial notion that addiction was a disease. She had the full support in Mr. Adelson in her endeavors, at least in part due the fact that a deceased son from his first marriage had a history of drug abuse. “Sheldon is everything to me,” she says. “He is my best friend, as I know I am to him, and he is a ‘mensch.’ He claims that I’m an angel and I say he is the ‘wind beneath my wings.’ In any case, we are on a magnificent flight together.”
In 2000, the couple opened the Dr. Miriam and Sheldon G. Adelson Research Clinic in Las Vegas. Despite the fact that the couple’s fortune was last tallied at $21.5 billion, Dr. Adelson still puts on the lab coat every day, conducting research on treatment, collaborating on studies of genetic predisposition to addiction, and working directly with patients. “I went to visit her once at the clinic in Tel Aviv,” says Zvi Galil, the former president of Tel Aviv University. “I had to wait 25 minutes to see her because she was personally seeing to the treatment of an addict. That’s amazing, considering her position.” Indeed, one half of the world’s richest Jewish couple has remained at the front lines of addiction treatment, a fight she joined long before she had money enough to never work again.
“Money is not the most important thing in life,” she says. “For my husband, money is only a benchmark to measure his success as an entrepreneur and visionary. I studied medicine and worked as an Internist and Emergency Room physician. I fought to save lives of young and old and had survivors, and, unfortunately, I had people die in my arms. My priorities in life are my family, to be a good mother and a loving wife. Money is down on the list of my priorities. That is why I have no problem to change my expensive suit for the white ‘lab coat.’ Ask me which one I prefer, and I will tell you that with no doubt, it is the white one.”
She is quite proud of what the clinics have done. “My clinics have achieved far above the goals I had for them,” she says. “Saving a drug addict is the equivalent of saving about 20 people. Treating one drug addict reduces his criminal activity, reduces his arrests, reduces his appearances in court, reduces his time sitting in prison, reduces his injecting drugs, reduces him being infected with HIV & Hepatitis C while sharing needles, and reduces his infecting others if he is already infected. It also improves his general medical condition, improves his behavior at home and in the environment, improves his work habits, and has a positive impact on his family by having a normal person around them. By treating one person, we can save many lives, and a mission like that is very much fulfilling.”
In politics, the Adelsons have acted in concert. When asked about their parallel moves, Dr. Adelson acknowledges the team playing. “Sheldon and I share the same vision and beliefs, although we come from two different backgrounds,” she says. “We are in full agreement on the causes we support, whether they are helpless people, drug addicts, or young people looking for roots in Israel. We don’t have arguments, or long discussions; it’s a quite fast discussion bearing in mind our common values.”
If political support were a blackjack table in one of Adelson’s casinos, the couple would come out winners. They’ve supported all of Senators Roy Blunt (R-MO, $2,400 each), Dean Heller (R-NV, $7,500 each), Scott Brown (R-MA, $2,400 each), Pat Toomey (R-PA, $2,400 each), and Mark Kirk (R-IL, $2,400 each); Congressmen Eric Cantor (R-VA, $2,400 each), Joe Heck (R-NV, $9,900 each), Mark Amodei (R-NV, $2,500 each), Virginia Fox (R-NC, $4,800 each); and former president George W. Bush ($2,000 each).
Of course, they have also lost some bets. Aside from Gingrich, they have supported the losing candidacies of Sue Lowden for U.S. Senate ($7,200 each), and the presidential campaigns of John McCain ($2,300 each) and Rudy Giuliani ($2,300 each). Their identical donations in the fall of 2011 to the National Republican Congressional Committee ($30,800 apiece) and Republican National Committee ($61,600 apiece) might very well end up losing bets as well. News reports of their Gingrich donations included the somewhat ridiculous notion that Dr. Adelson’s $5 million came with the condition that the money only be spent on positive ads about Gingrich, not negative ads about the other candidates. The Adelsons are playing for keeps; it is absurd to suggest that wouldn’t support winning by any means.
The $10 million to Gingrich firmly established the Adelsons’ status as “megadonors” — before which they had both only given the legal maximum of $2,500 to Gingrich’s campaign. But calling someone a megadonor requires a degree of perspective. Ten million for Sheldon and Miriam Adelson is literally pocket change. “Look, this is a substantial donation, but it’s not really substantial for the Adelsons,” says Fred Zeidman, a major Republican fundraiser. “And Miri has felt every bit as indebted to Newt for his support of Israel as Sheldon has. They’ve funded him since the day he walked out of Congress.” Indeed: that includes $7.7 million in donations to American Solutions for Winning the Future, a Gingrich-group, between 2006 and 2011. “Keep in mind, too, that this isn’t a lot when you look at their philanthropy,” adds Zeidman. “In fact, I think you have to consider this just another small part of their philanthropy. That, and their concern for the security of Israel.”
The Adelsons’ philanthropic giving does make their political donations seem small by comparison. They have support Taglit-Birthright Israel — which offers ten-day trips to Israel to Jewish adults between 18 and 26 — by donating more than $100 million to the organization since 2007. In addition, they have given $25 million to the Holocaust memorial organization Yad Vashem; $25 million to a Jewish high school in Summerlin, Nevada; $20 million to Hebrew SeniorLife in Dedham, Mass; and $5 million to a Jewish elementary and middle school in Newton, Mass.
Sheldon Adelson is Jewish, but he had only visited Israel a handful of times before their marriage. It seems clear that Dr. Adelson helped bring her husband to the Israeli cause, which has also resulted in the Adelson Family Foundation, which focuses primarily on programs that benefit the state of Israel and the Jewish people. The Adelsons also own Israel’s largest newspaper, the stridently pro-Netanyahu Israel Hayom. According to The Atlantic, the paper is considered “the Fox News of Israel.” Finally, the couple sponsors the Adelson Medical Foundation, which focuses on promoting a collaborative approach to medical research.
“While she is much more approachable in many ways than Sheldon is, she is also intense and passionate about things she believes in,” says Jon Ralston of the Las Vegas Sun, who first reported news of the super PAC donations. “When I finally convinced Sheldon to come on my television program in 2010, she came with him — and not just to the studio. She was right beside the camera, a few feet away, looking intently for the entire interview. I was afraid if I asked too aggressive a question she was going to walk right onto the set with us.”
Just how equal this partnership truly is can be understood when one looks at the couple’s ownership of stock in Las Vegas Sands, their publicly traded holding company. Miri Adelson owns 26.9% of LVS while Sheldon — the front man for the operation — owns just 26.3%. Their combined ownership is down from earlier this decade, in part because the Adelsons were forced to sell shares in 2008 in order to raise $1 billion to pump back into the company in order to forestall a looming debt default. At the height of the financial crisis, the couple’s fortunes had dwindled to a mere $400 million, declining some $24 billion in the span of a single year. A rebounding stock market — and stunning success for LVC in Macau and Singapore — have seen their fortune rebound nearly all the way back to pre-crisis levels. (Dr. Adelson also worked with the Macau government to help them develop their own addiction clinic in recent years.)
The Marina Bay Sands in Singapore is almost unbelievable in its sheer scale. Costing $5.6 billion, much of it spent during the financial crisis, the complex includes three 55-story hotels, 40,000 square feet of “sky park”, two theaters, 50 restaurants, and 800,000 square feet of retail. And the Venetian and Palazzo in Vegas is the largest hotel in the world at 18.5 million square feet. The Adelsons do not do anything on a small scale. When Miriam turned 50, according to a reporter from the New York Times, her husband flew more than 100 friends from Israel to Las Vegas for the party. (Together with LVS, Adelson owns 14 planes, which the casino magnate has used as a competitive differentiator by flying high rollers in to Vegas.)
Dr. Adelson can lay claim to more than just being a partner in politics and philanthropy. It was she who came up with the idea for the Venetian resort and casino, the creation of which put LVS on the road to gambling world domination and fueled the overall renaissance of Las Vegas itself. “We thought Venice was a very unique city,” she told a reporter in March 2011. “It’s romantic and historical; you walk through the streets and you feel that there were so many generations who walked those very streets before you. It’s a very special city. I told him, ‘if you can bring the romantic atmosphere of Venice with all the luxuries that can only be found in Las Vegas, then it can be a winner.’ But then again, there were other ideas I gave him which he didn’t listen to at all.”
When she offers such self-deprecation, Dr. Adelson, whose striking presence is only enhanced by long platinum blond locks and a thick Israeli accent, is just being coy. Sheldon Adelson may be a singular persona in the wild and wooly world of gambling, but at home, he is one half of a very equal partnership.