Call it the Adelson conundrum: What happens when the guy who acts as if he owns the room really does?

In March at TribeFest, the annual gathering of young adults organized by the Jewish Federations of North America at the Venetian hotel in Las Vegas, Sheldon Adelson walked in on a debate between Matt Brooks, who directs the Republican Jewish Coalition, and his counterpart at the National Jewish Democratic Council, David A. Harris.

Adelson, the multibillionaire who owns the Venetian, berated Harris for six minutes, describing President Barack Obama as a “crybaby” who should be in diapers, according to several people present.

Sheldon and Miriam Adelson photo/jta-flash90-olivier fitoussi

One of the event’s organizers, who declined to be named, said the only reason Adelson was able to monopolize the conversation that way was because he  “owned the room, literally.”

That same sense of entitlement could be driving the 79-year-old Adelson’s conversations with Mitt Romney, the presumptive Republican nominee for president.

This week, the Daily Beast/Newsweek reported that Adelson was pressing Romney to speak out publicly in favor of the release of convicted spy Jonathan Pollard, to commit to moving the U.S. Embassy in Israel to Jerusalem from Tel Aviv, and to declare the Palestinians as unwilling to make peace. Romney, the report said, is resisting.

Through political action committees, Adelson and his wife, Miriam, have funneled $10 million toward Romney’s election effort. Adelson has said he’s willing to spend up to $100 million to defeat Obama.

Those close to Adelson say politics are a small part of what makes him tick.

“He is passionately committed to Jewish life and living, and to Israel,” said Elliot Karp, the director of the Las Vegas Jewish Federation. “And he is no more or less polarizing than anyone else who gives his opinions.”

Adelson has given nearly $100 million to Birthright Israel, the program that brings Jews aged 18-26 to Israel for free. He revived the fortunes of the Yad Vashem Holocaust memorial in Jerusalem with a $25 million gift in 2006. He has established a $4.5 million Jewish studies center in his name at the Shalem Center, a right-wing think tank in Jerusalem. His relatively smaller donations have helped bolster groups such as the Zionist Organization of America and The Israel Project.

“The true story is that the amount of money he spends on politics is dwarfed by what he gives to philanthropy,” Brooks said. “[The couple is] the single most important philanthropists in the Jewish community, in terms of Birthright, Yad Vashem and medical research.”

Adelson is the 15th richest man in the world, according to Forbes, with an estimated worth of $25 billion.

Miriam Adelson, an internist from Israel who specializes in drug addiction, is his second wife. He met her on a blind date in 1989, a year after he divorced his first wife, Sharon.

Adelson, a product of a working-class family in Dorchester, Mass., who made his first fortune organizing computer trade shows, already was leaning right, but Miriam helped sharpen his views, particularly relating to her native Israel.

The confluence of Adelson’s three major interests — Jewish philanthropy, Republican politics and the casino business, which is how Adelson became one of the world’s richest men — has become one of the preeminent narratives of this election campaign.

Some frustrated Jewish Democrats believe the Jewish community is unduly influenced by its single largest donor.

“It’s very intimidating,” said Steve Rabinowitz, a leading public relations consultant to Jewish and Democratic causes. “Where he’s given money, he’s given extraordinary amounts of money, and I’ve seen it firsthand.”

Adelson’s publicist, Ron Reese, did not return multiple requests for comment.

For his part, Adelson is unapologetic about using his money to influence policy.

“I’m against very wealthy people attempting to or influencing elections,” he told Forbes in February. “But as long as it’s doable I’m going to do it. Because I know that guys like Soros have been doing it for years, if not decades,” he said, referring to the left-wing financier George Soros, who also is Jewish.

Democrats scoff at the comparison, noting that Soros in this election cycle has pledged $2 million to help Obama’s re-election — one 50th of the amount that Adelson has said he’s willing to spend.

The mixture of Adelson’s politics and charitable giving is not new. In December, addressing a Chanukah gathering in Israel of hundreds of Birthright participants, Adelson championed Newt Gingrich after the then-Republican candidate for president said the Palestinians were an “invented people.” At the time, Adelson was the single biggest backer of Gingrich; he and his wife gave $16.5 million to the campaign.

Birthright did not return a request for comment for this story.

In 2007, Adelson broke with the American Israel Public Affairs Committee over its support for a congressional letter calling for a massive increase in funding for the Palestinian Authority. Adelson previously had been one of AIPAC’s major backers, helping to fund its new Washington headquarters.

He has a reputation as a nitpicker: The staff of Freedom’s Watch, which Adelson founded before the 2008 election to champion President George W. Bush’s Iraq War policies, said Adelson’s day-to-day micromanaging caused the organization to founder. Freedom’s Watch no longer exists.

Adelson can hold a grudge. He fired Shelley Berkley, his legislative director in the 1990s, over keeping the unions he reviles at the casinos. Berkley went on to become one of Israel’s most strident defenders in Congress and the Nevada Democrat is now running for the U.S. Senate, but Adelson’s opposition to her has not waned. He and his wife have maxed out donations to her opponent, incumbent Sen. Dean Heller, a Republican.

But Adelson can also be forgiving. Despite repeated clashes with the Las Vegas Jewish Federation for what he calls its wastefulness, he is now its biggest donor, matching every new donation and every increase over the previous year’s donations.