The effort was aimed at the U.S. Supreme Court’s Citizens United decision and called attention to the massive spending by outside groups this election year. While President Obama and GOP presidential candidate Mitt Romney have both welcomed the help of super-PACs that can take unlimited and anonymous political donations, their efforts are expected to give Romney a funding advantage.

Republicans argued the vote was political posturing by Democrats and said it favored unions over corporations.

“This bill falls short, the American people will see it for what it is: political opportunism at it’s best and political demagoguery at it’s worst,” Sen. John McCainJohn Sidney McCainRubio asks Army to kick out West Point grad with pro-communist posts The VA's woes cannot be pinned on any singular administration Overnight Defense: Mattis offers support for Iran deal | McCain blocks nominees over Afghanistan strategy | Trump, Tillerson spilt raises new questions about N. Korea policy MORE (R-Ariz.) said. “The union’s ground up, pyramid structure leads me to believe it will be exempt from Disclose Act.”

McCain said he hopes that next time Democrats take on campaign finance reform — something he’s worked on throughout his political career — they get a Republican on board before “wasting Senate time."