"I know what I'm talking about when I talk about the power of the lie with a lot of money behind it," he said, referring to his own presidential campaign, in which an outside group, Swift Boat Veterans for Truth, spent more than $23 million criticizing his military record, according to the FEC.
Democrats have rallied around the campaign finance reform, and specifically disclosure this election, in part because they have been on the losing end of the Supreme Court's decision. Outside groups, especially secretive 501(c) nonprofits, have consistently spent on behalf of Republicans. In 2010, these groups spent considerably more than Super PACs, and spent five times more benefitting conservative candidates than liberal ones, according to the Center for Responsive Politics.
In that election, the Center estimates 45 percent of all outside spending came from unnamed donors.
Watchdog groups like the Sunlight Foundation say the amount of anonymous donations in elections creates an environment where voters don't even know who is behind the ads they are inundated with.
"The messenger is as important as the message," says Lisa Rosenberg, a government affairs consultant for the Sunlight Foundation.
Seth Cline is a reporter with U.S. News and World Report. Contact him at firstname.lastname@example.org or follow him on Twitter.
Lauren Fox is a Congressional reporter with U.S. News and World Report. Contact her at email@example.com or follow her on Twitter.