"I promise you, there will be huge scandals because there's too much money washing around, too much of it we don't know who's behind it and too much corruption associated with that kind of money," McCain continued. "There will be major scandals."
McCain coauthored with then-Sen. Russ Feingold (D-Wis.), legislation that limited the amount of money individuals could give to political organizations. The Citizens United case overturned part of that legislation. In the ruling, the Supreme Court said Congress shouldn't be allowed to limit the amount corporations, unions and similar entities gave to campaigns.
Since the ruling and the rise of super-PACs during the 2012 election cycle, McCain has been an outspoken critic of excessive campaign donations.
In late February, Feingold said that super-PACs were making the Supreme Court increasingly "squeamish" and that sooner or later the Citizens United ruling would be reversed in some way.