Outside groups pumped nearly $12 million into Missouri’s U.S. Senate election this year between Roy Blunt and Robin Carnahan. Much of the spending was negative and it was made possible by a January Supreme Court decision that opened the floodgates to unlimited spending by corporations and unions on political campaigns.

The single largest spender was American Crossroads. The group, co-founded by Karl Rove, former President Bush’s chief political operative, and Ed Gillespie, the former chairman of the Republican National Committee, spent more than $21 million on ads attacking Democratic candidates across the nation this election season.

The group spent nearly $2.7 million into the race to replace retiring U.S. Senator Kit Bond. That’s in addition to the $1.1 million spent by a sister group, Crossroads Grassroots Policy Strategies. Crossroads GPS is noteworthy in that it operates under a section of the tax code that allows the group to keep the names of its donors secret — an option the organization has exercised.

The two groups’ combined $3.8 million in independent expenditures in the Missouri race stands as the largest pro-Republican investment in the race, which Blunt won handily.

The numbers come courtesy of the Sunlight Foundation, an organization that tracks money in politics.

The group, founded in 2005 by Washington attorney Michael R. Klein, has received major donations from the Rockefeller Family Fund and eBay founder Pierre Omidyar.

– Missouri Digital News