Maine's U.S. Senate race is a battle between not two, but three candidates vying to replace retiring Senator Olympia Snowe: Republican Charlie Summers, Democrat Cynthia Dill, and former Governor Angus King, a left-leaning independent. Despite outside groups like the U.S. Chamber of Commerce spending millions attacking King, he retains a sizable lead -- but the complex, multi-million dollar web of outside spending has made Maine's U.S. Senate race one of the most interesting in the country.

One Wisconsin Now and theGrio have uncovered that the Milwaukee-based Einhorn Family Foundation is the "private family foundation" that funded controversial billboards in Milwaukee which warned: "VOTER FRAUD IS A FELONY! 3 1/2 years and a $10,000 fine." The billboards were denounced as voter suppression by Mike Wilder, director of the African-American Round Table, and other community groups. The billboards were put up in largely African-American and Latino communities in Milwaukee, Cleveland and Columbus by media behemoth Clear Channel, but the client remained anonymous.

- Connor Gibson, Greenpeace

Earlier this year internal documents from the Heartland Institute, a major hub of climate change denial and right-wing extremism, were publicly leaked. The documents exposed the Heartland Institute's funders and strategies for attacking climate science, and led to a mass exodus of Heartland's corporate funders.