Last week, when Mitt Romney claimed not to have seen an attack ad his campaign had produced, he was no doubt trying to blame his super PAC, Restore Our Future, for coming up with it. Whether or not the former Massachusetts governor was being truthful—one can imagine that, in a fast-moving campaign, candidates only passively approve the messages their surrogates put out—the incident underscored the way super PACs, which are barred from coordinating directly with the candidates they are supporting, have come to dominate the political landscape.