Outside of public radio, which I don't count for a variety of reasons, liberal talk does not succeed. IMHO it is because in general the liberal mindset is more about political positions, and the conservative side is more about political ideas. As the previous poster stated, if you know your positions and the host agrees with them, why listen?
There's a guy on MSNBC, Steve Karnacki (sp?), whom I find quite intelligent, and obviously liberal, who digs down into the meat of a topic, rather than just shooting off his mouth. I'd love to hear him on the radio... he does great interviews and reports news, not just political strategery.
OTOH, I probably agree with Hannity on 90% of issues, but I can't listen to him.
Ultimately, it's the ability to inform, entertain and enlighten. Again JMHO.
"it is because in general the liberal mindset is more about political positions, and the conservative side is more about political ideas."
I have a different take.
It is mostly demographics, those who access AM radio and available audience in the daytime.
All of these factors point to an older, more conservative audience peppered with many retirees.