Here is an article in American Thinker, a media outlet sympathetic to Rush Limbaugh, that tries to explain his success. Much of what the article says is true, for example Rush is a heck of an entertainer and he is knowledgeable about his main subject: domestic politics. What the article says is true but it misses the main point.
The main reason Rush (and Sean Hannity, Michael Savage, Laura Ingraham, etc.) are successful on talk radio is that they provide something not generally available in the mainstream media - conservative thought and advocacy. Its very lack of availability in the MSM creates a market for their wares.
Attempts to produce liberal talk radio have failed dismally (c.f., Air America). Liberal talk radio fulfills no need since the MSM, plus PBS and NPR, have the lefthand part of the political spectrum covered already, leaving no demand for additional product in most markets.
If there were such demand, radio would be delivering that left-leaning product and reaping the advertising dollars that follow listeners. In fact, liberal talk radio does exist in a few limited markets like San Francisco and some ethnic stations.
