There has been considerable discussion recently about the success of conservative talk radio (e. g., Rush Limbaugh, Michael Savage) and the non-success of liberal talk radio (Air America, etc.) That this gap exists is not in question, the question is why it exists. What follows is my view, and the view of the other DrC is also noted.
I believe conservative talk radio is successful because it articulates the views of many listeners who do not find those views championed in the mainstream media (MSM). The MSM is overwhelmingly liberal in editorial content.
Liberals need only watch or listen to the network news, or PBS or NPR to hear their views reflected in both news and editorial opinion content. Thus, liberal talk radio competes with almost the entire MSM plus the noncommercial broadcasters. Conservative talk radio only competes with Fox Cable News, some online sites and a handful of conservative magazines (e. g., National Review, The Weekly Standard).
In other words, the issue is one of supply and demand. Presumably there is roughly equal demand for liberal and conservative opinion since the electorate is nearly evenly divided politically. What isn't equal is supply; liberals have many more sources of supply than do conservatives. Since conservatives get concentrated into relatively few outlets, those outlets have very high viewer- and listenership. Thus, Fox News channel gets higher ratings than its cable news competitors and the stations with conservative talk shows do well too. Somewhere, I imagine the ghost of Adam Smith is laughing quietly.
The other DrC opines that perhaps hip-hop or rap music is the "talk radio" of the left, with its persistent themes of violence, misogyny and alienation. Perhaps those on the left prefer listening to music lyrics (instead of political rants) with which they agree. I suspect this view has merit too.
Gentle readers, feel free to contribute your own opinions on this topic.