Sixty-two percent of funds raised by two conservative groups associated with former Bush adviser Karl Rove have come from mystery donors, a statistic that shows the increasingly important role being played by nonprofits in a post-Citizens United political world. American Crossroads, a super PAC, and Crossroads Grassroots Policy Strategies, a nonprofit, were founded in 2010 by Rove and another former Bush adviser, Ed Gillespie. Together, they raised $123 million through the end of 2011, according to an iWatch News review of Federal Election Commission data and Internal Revenue Service filings. Of that sum, $76.8 million, or 62 percent, went to Crossroads GPS, which is a nonprofit, “social welfare” group organized under section 501(c)(4) of the U.S. tax code. Like American Crossroads, Crossroads GPS can pay for advertising that attacks political opponents by name and urges viewers to vote against them. But unlike the super PAC, GPS is prohibited from making politics its “primary purpose,” according to the IRS, a rule that these politically active nonprofits have interpreted to mean they can spend up to 49 percent of their funds on such advertising.