Back in April, I wrote Hushed Money:Could Karl Rove’s new 527 avoid campaign-finance disclosure requirements?.
Today Politico reports that the money started coming in only after American Crossroads created a related 501(c)(4):

Though American Crossroads will be required to disclose to the IRS its donors and expenditures for June in about three weeks, Law would not immediately reveal the precise fundraising division between it and Crossroads GPS, which he said was incorporated about four weeks ago under section 501(c)4 of the IRS code. That section of the code requires far less disclosure and allows groups to withhold information on individual donors, which Law conceded was appealing for some of GPS’s donors. “I wouldn’t want to discount the value of confidentiality to some donors,” said Law.