During the 2008 election cycle, Mr. Adelson became recognized as a top-tier donor to the right and a moneyed villain to the left. He was the primary financier of a conservative nonprofit group, Freedom’s Watch, which trumpeted plans to spend as much as $200 million on the presidential election. Those plans, however, fizzled as internal problems paralyzed the organization, with Mr. Adelson micromanaging the group’s efforts, Republican operatives familiar with the organization said at the time. The group still spent about $30 million through early 2008, almost all of which came from Mr. Adelson, according to the operatives.

Today, the Venetian and the adjoining Sands Convention Center have become default destinations for Republican events in Las Vegas.

“I call it the Republican headquarters on the Strip,” said Jon Ralston, the political columnist for The Las Vegas Sun.

The Venetian will also be the official headquarters hotel for Saturday’s Nevada presidential caucuses. And in deference to observant Jews, the Clark County Republican Committee has scheduled a special caucus on Saturday night at the Adelson Educational Campus, a Jewish school financed by the Adelsons, six hours after the rest of the state is done caucusing.

When it came time to picking sides for this year’s Republican presidential nomination, Mr. Adelson made clear to friends early on that if Mr. Gingrich decided to run, he would back him. When Mr. Gingrich’s campaign faltered, friends who supported other candidates put pressure on Mr. Adelson to stay out of the race.

Nevertheless, Mr. Adelson made an initial $5 million contribution to Winning Our Future, a pro-Gingrich super PAC, before the South Carolina primary, which proved pivotal in Mr. Gingrich’s victory there.

Fred Zeidman, a Texas energy executive active in Jewish and Republican circles, said he talked to Mr. Adelson early last week, before it became public that Mrs. Adelson, 66, had also donated $5 million to the super PAC. Mr. Adelson told his friend that he was going to give more money and seemed to signal that he was willing to keep it flowing.

“I think what he’s trying to say is, ‘Newt ain’t going away, and I’m going to make sure of it,’ ” Mr. Zeidman said.