Adelson, whose net worth approaches $25 billion, has suggested that he is willing to spend up to $100 million to defeat Mr. Obama...
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.
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...
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.
http://www.nytimes.com/2012/06/17/us/politics/sheldon-adelson-injects-more-cash-into-gop-groups.html