Those nonstop ads in Ohio come at a cost. According to a new analysis of campaign-spending disclosures by non-affiliated organizations, outside groups spent over $500 million in October alone. The top three spenders—American Crossroads, Crossroads GPS, and Restore Our Future—spent $173 million alone. All three groups support conservative causes, and the bulk of the money went to ads that target President Obama. But the Democrats also raised big bucks: the pro-Obama super PAC Priorities USA brought in $75.5 million in October.