A new analysis of the U.S. Chamber of Commerce’s donations show just why Obama has been attacking the group so hard. The chamber, which is the world’s largest nonprofit lobbying group, receives millions of donations from big businesses and then turns the money into a powerful tool to fight regulation of those industries. For example, insurance companies poured at least $10 million into the chamber’s coffers while the Obama administration was fighting for health-care reform. Now the group has turned to electoral battles, spreading its largesse almost exclusively to Republican candidates. Its donations are anonymous.