Americans for Prosperity is a non-profit 501(c)(4) "social welfare" organization founded in 2004 with major support from the Koch brothers.  AFP is "committed to educating citizens about economic policy and mobilizing those citizens as advocates in the public policy process."  According to the Sunlight Foundation Reporting Group's "Follow the Unlimited Money" (+), Americans for Prosperity spent $33.5 million on independent expenditures opposing President Obama.