Demographics?

[Femmebott]

Where could I find information about the types of people that watch certain political analysts? I think what I am asking is where could I find statistics on Glenn Beck's viewers? Or Keith Olbermann's...
Are they mostly conservative middle class? White? Black? Liberal?

[Mader]

Industry mags/sites Broadcasting & Cable, for example

Advertising mags/sites Advertising Age, for example

Lots of data is not available unless you are a member, in the industry, or a client, but this is a place to start.