For a brief, giddy moment, Sean Noble—a little-known former aide to an Arizona congressman—became one of the most important people in American politics.

Plucked from obscurity by libertarian billionaire brothers Charles and David Koch, Noble was tasked with distributing a torrent of political money raised by the Koch network, a complex web of nonprofits nicknamed the Kochtopus, into conservative causes in the 2010 and 2012 elections.

Noble handed out almost $137 million in 2012 alone -- all of it so-called dark money from unnamed donors -- from his perch atop the Center to Protect Patient Rights, a group run out of an Arizona post office box. ........................