Not a formal adviser but ... Matt explains:
[W]hat you hear if you talk to people in left-of-center national security circles in Washington is that one of Berger's informal responsibilities is basically to get in touch with former Clinton administration foreign policy hands and warn them in no uncertain terms that if they back Barack Obama, Clinton will win anyway and those who supported her rivals will pay the price.
Just an enforcer, a man who'll do the dirty work necessary to intimidate and hound any dissenters from the Clinton machine. Remind me how he got into trouble in the first place?