Annenberg Public Policy Center calculates dollars spent by third-party groups on deceptive TV ads attacking or supporting the presidential candidates

Drawing on spending estimates from Kantar Media CMAG and the fact-checking of the major fact-checking sites, the Annenberg Public Policy Center has found that from April 10, 2012 when Mitt Romney became the presumptive nominee of the Republican party (according to Kantar Media CMAG) through September 20, 2012, an estimated 27.8 percent of the dollars