Tip of a very large iceberg, I suspect.

Must-read Bloomberg BNA: “The insurance company Aetna confirmed June 14 that it donated about $7.8 million to two major Republican-leaning organizations—the U.S. Chamber of Commerce and American Action Network—which have sponsored tens of millions of dollars worth of political ads but have never disclosed their funding sources. The revelation—which came due to an accidental filing by Aetna—was significant because few, if any, political donations from large, public corporations have been revealed previously….’We support organizations and candidates who share our views on how to fix the problems facing our health care system, as well as our country,’ [Aetna President] Bertolini said. ‘We fully comply with all federal and state disclosure requirements.’…The Chamber spent over $30 million on television ads in the 2010 congressional elections—nearly all of it backing Republican candidates or attacking Democrats.”