Today the FEC posted this draft proposed rulemaking on the 527 issue. This document is essentially what the general counsel believes should be the starting point for rulemaking, subject to notice and comment by others and ultimate decision by the six FEC commissioners.
I have not had a chance to even print the document yet, so analysis will have to come later. You can find some preliminary analysis by Bob Bauer here. In somewhat related news, Americans Coming Together has withdrawn its request for an advisory opinion on its activities. (Thanks to Marty Lederman and others for pointers to these materials.)