Soon after the Citizens United decision (the same year this post was written) and other legal developments, the Koch brothers became very active at the center of a network of conservative, politically active 501(c) groups that aren’t required to disclose their donors. The groups, including Americans for Prosperity and Freedom Partners Chamber of Commerce, have collectively spent hundreds of millions of dollars working for or against candidates and/or giving money to other groups doing that kind of work. Nobody knows how much money the Kochs themselves are providing to this network. George Soros, on the other hand, has been very generous to Democratic super PACs, such as Priorities USA Action, which must publicly list their donors. Because we don’t know how much money the Kochs are providing, it’s virtually impossible to compare them with Soros or anyone else. A list of top contributors is here — but again, the list doesn’t include the Kochs because many of their checks are written to groups that don’t have to tell us where their funds are coming from.