Foreign money and American elections are like fire and water, orange juice and toothpaste, Yankees fans and Red Sox fans: The two don't mix. At least they haven't for nearly 50 years, when the federal government banned foreigners from giving or spending any money on local, state, and federal elections.

But for the secretive nonprofit groups pumping hundreds of millions of dollars into the 2012 elections, the rules are different. These outfits, organized under the 501(c) section of the US tax code, can take money from foreign citizens, foreign labor unions, and foreign corporations, and they don't have to tell voters about it because they don't publicly disclose their donors. What's more, with a savvy attorney and a clean paper trail, a foreign donor could pump millions into a nonprofit without even the nonprofit knowing the money's true origin.