I started looking for David Brock info and found this article. It has Brock, SEIU, Media Matters Soros, Media Matter and even "cards" in it.
Even has a law firm connected to Obama.

http://www.redstate.com/laborunionreport/2014/04/16/seiu-petitions-obama-nlrb-unionize-lefts-media-matters/

"According to the National Labor Relations Board’s website, Media Matters has hired the high-priced, management-side law firm of Perkins Coie,,Although former Obama White House Counsel Bob Bauer is a partner in the firm, Perkins Coie’s website boasts of helping employers in all aspects of traditional labor law" I just don't have enough understanding of this to know if it could be of any value in research.

Interesting tidbit on lawfirm Perkins Coie

http://www.conservativehq.com/article/25713-what-fbi-should-be-investigating-death-dnc-staffer-seth-rich "Instead of the FBI’s computer crimes forensics section, the DNC and its law firm Perkins Coie choose instead to turn to CrowdStrike"