HuffPo: “Through July 26, politically involved groups that do not disclose their donors have spent at least $172 million on campaigns that include television, radio and Internet advertising, according to a Huffington Post review of FEC reports, advertising buys, press releases and news stories. Total spending by these groups is likely far greater, since they are required to report only a fraction of their spending to the FEC. Politically involved independent groups that publicly disclose their donors, including super PACs, have spent $174 million so far this election cycle.”