The success of GOP and Tea Party-backed candidates in the 2010 U.S. midterm elections was enabled by a massive influx of secretive spending thanks to the Supreme Court’s ruling in Citizens United v. FEC.

A new analysis by the Sunlight Foundation identified $126 million in unrestricted funds spent during this midterm without any disclosure of whose money it was. That figure represents more than a quarter of the total $450 million spent by outside groups on the midterms.

Sunlight Foundation notes that:

The two leading GOP shadow groups, American Crossroads and Crossroads GPS – both founded and guided by GOP veterans Karl Rove and Ed Gillespie – are reportedly “gloating” over their influence on the elections. The two groups spent more than $38 million on attack ads and misinformation campaigns to defeat Democratic candidates.

NBC News reports that “a substantial portion of Crossroads GPS’ money came from a small circle of extremely wealthy Wall Street hedge fund and private equity moguls.”

The result? “Republican candidates won nine of the 12 Senate races and 14 of 22 House races where American Crossroads and Crossroads GPS spent money.”

The Citizens United ruling opened the floodgates for unrestricted Wall Street and corporate money to pollute U.S. elections, creating a recipe for negative attack ads to demoralize voters and secure wins for business-friendly candidates.  

Sunlight Foundation senior writer Paul Blumenthal notes: “the Supreme Court’s Citizens United ruling allowed this election to be the costliest and least transparent midterm in recent history.”

Unless Congress acts to require disclosure of funders who bankroll the front groups and attack ad squads, the 2012 presidential race and every U.S. election to come will be tainted by unaccountable special interest money.

That’s bad for American democracy, no matter what party you associate with.