New G.O.P. Help From Casino Mogul

Mr. Adelson — who has already donated more than $30 million this year to “super PACs” backing Newt Gingrich, who dropped out of the presidential race last month, and Mitt Romney, who is now the Republicans’ likely nominee — is quickly expanding his giving to a variety of Republican-leaning organizations, including tax-exempt issue advocacy groups that are expected to spend most of the outside money in this year’s campaigns.

He has committed at least $10 million to the Crossroads Grassroots Policy Strategies, founded by Karl Rove, according to people with knowledge of his donations. He has discussed contributing another $10 million to groups aligned with Charles and David Koch, the billionaire oil and chemical executives who founded Americans for Prosperity, another issue group.

Such organizations, known as 501(c)(4) groups after the section of tax law under which they are organized, are not allowed to engage in full-time campaign activity. And unlike super PACs, they are not required to disclose their donors. But the groups have already spent tens of millions of dollars on issue ads, much of it on behalf of Republican candidates or against President Obama.

Mr. Adelson has also contributed $5 million to Young Guns, a super PAC with ties to the House majority leader, Eric Cantor, and $5 million to the Congressional Leadership Fund, another super PAC backing House Republicans. Details of the contributions were reported on Saturday by The Huffington Post.

Legal and regulatory shifts have opened new avenues for the wealthy to influence campaigns, and spending by outside groups has more than doubled over the 2008 campaign, according to the Center for Responsive Politics. Mr. Adelson, whose net worth approaches $25 billion, has suggested that he is willing to spend up to $100 million to defeat Mr. Obama and elect Republicans this year.

“He’s fully committed to beating Barack Obama,” said Fred S. Zeidman, a Texas energy executive and a friend of Mr. Adelson’s. “We think ‘$100 million, wow!’ But it’s a meaningless amount of money to him.”

The unusually heavy flow of money has drawn concern not just from liberals and government watchdog groups, but even from some Republicans.

In an interview posted online on Friday, Senator John McCain, Republican of Arizona, and an ally of Mr. Romney, assailed Mr. Adelson’s contributions to Restore Our Future, suggesting that they had effectively allowed foreign money into the presidential race. Foreign citizens are prohibited from making direct contributions to candidates and political committees.

“Obviously, maybe in a roundabout way, foreign money is coming into an American campaign,” Mr. McCain said in the interview with PBS.

Beyond his opposition to Mr. Obama, Mr. Adelson is deeply involved in Israeli politics and is an avid backer of Republican Jewish organizations. His company, Las Vegas Sands, is under federal investigation for possible violations of a federal antibribery law linked to its expansion in the Chinese gambling district of Macau, a major source of Mr. Adelson’s income. The company has said the investigation stems from the accusations of a disgruntled former employee.

During the Republican primary, Mr. Adelson and his wife, Miriam, poured more than $20 million into Winning Our Future, a super PAC supporting Mr. Gingrich, a longtime friend and ally who shares Mr. Adelson’s hawkish views on Israel. Following Mr. Gingrich’s withdrawal, Mr. Adelson committed $10 million to a super PAC backing Mr. Romney. He has also contributed $5 million to the Congressional Leadership Fund, a super PAC in support of Republican candidates.