A show's purpose is **NOT** to influence public opinion.
The purpose of a tv or radio show is to hold the attention of as many people for as long as possible so the network can charge confiscatory advertising fees to the sponsors.
And who wants to listen to a bunch of negative, pessimistic, hate filled, doom and gloomers for hours ..who, except a few wackos ?
+ learned.
I think this is the bottom line on the question of "Why no liberal Rush?" Rush Limbaugh is first and foremost, entertaining. He is funny. Insightful. Sometimes dumb, but mostly entertaining.
Hannity, Medved, Laura Ingraham, similarly do their own things but do not spread hate, despite the biased disatortions of the Left.
AirAmerica was just angry and vituperative, all about hating Bush. As entertaining as a car accident on the freeway. You almost involuntarily slow down to look but don't want to linger, and you don't go back. I doubt the Bob Shrums of the world will be much of an improvement.