Who is Advisor B?

This statement in the indictment against Blagojevich suggests Obama was deeply involved in negotiations with Blagojevich.

On November 12, 2008, ROD BLAGOJEVICH talked with Advisor B. ROD BLAGOJEVICH discussed with Advisor B his idea for a 501(c)(4) organization. Advisor B stated that he likes the idea, but liked the Change to Win option better because, according to Advisor B, from the President-elect’s perspective, there would be fewer “fingerprints” on the President-elect’s involvement