Mr. Adelson

Mr. Adelson, 78, has decided to throw his wealth behind what had once seemed to be the unlikely presidential aspirations of Newt Gingrich. Now, in no small measure because of Mr. Adelson’s deep pockets, Mr. Gingrich is locked in a struggle with Mitt Romney heading into Florida’s Republican primary on Tuesday.

Mr. Adelson, by some estimates worth as much as $22 billion, presides over a global empire of casinos, hotels and convention centers whose centerpiece is the Venetian in Las Vegas, an exuberant monument to excess with canals, singing gondoliers and acres of slot machines. That fortune is a wellspring of financial support for Mr. Gingrich, who has benefited from $17 million in political contributions from Mr. Adelson and his wife, Miriam, in recent years, including $10 million in the last few weeks that went to a “super PAC” supporting him. 

The question of what motivates Mr. Adelson’s singular generosity toward the former House speaker has emerged front and center in the campaign. People who know him say his affinity for Mr. Gingrich stems from a devotion to Israel as well as loyalty to a friend. A fervent Zionist who opposes any territorial compromise to make way for a Palestinian state, Mr. Adelson has long been enamored of Mr. Gingrich’s full-throated defense of Israel. 

In December at an event in Israel for a charity he supports, Mr. Adelson made a point of endorsing Mr. Gingrich’s assertion that the Palestinians have no historic claim to a homeland. 

“Read the history of those who call themselves Palestinians and you will hear why Gingrich said recently that the Palestinians are an invented people,” Mr. Adelson said at the event for Birthright Israel, which takes young Jews on trips there. 

Mr. Adelson is hardly a household name. He avoids the limelight and rarely speaks to the press, remaining something of an enigma. He declined to be interviewed for this article, but he and his wife issued a statement saying friendship and loyalty are “our motivation for helping Newt.” 

Through interviews and a review of Mr. Adelson’s testimony in legal disputes with former associates, a portrait emerges of a formidable and determined striver who lifted himself out of childhood penury in working-class Boston. He has a sentimental streak — on one of his first trips to Israel, he wore the shoes of his late father, a cabdriver from Lithuania who was never able to visit there — and he has given hundreds of millions of dollars to Jewish causes, medical research and injured veterans. 

But his rise has not been without controversy. The Justice Department is investigating accusations by a former casino executive that Mr. Adelson’s operations in Macao may have violated federal laws banning corrupt payments to foreign officials. Also, a Chinese businessman accused Mr. Adelson of reneging on an agreement to share profits from the Macao project.