Very BIG stuff from Open Secrets:

There’s a new dark money game in town, one meant to further cover the tracks of tax-exempt groups that have provided major sums to help Republican causes in the 2010 and 2012 elections. Recent tax filings by the two largest “shadow money mailboxes” — groups that do virtually nothing but pass grants through to other politically active 501(c)(4) organizations, many of which have been big spenders on election ads benefiting the GOP — show their financial ties run far deeper than previously known.The groups, TC4 Trust and the Center to Protect Patient Rights — both of which have connections to the billionaire industrialist Koch brothers — have been playing a high-stakes game of hide-the-ball, disguising transfers of millions of dollars from one to the other behind a veil of Delaware limited liability corporations.