From Atrios:

Interview with liberal radio host Randi Rhodes.

RHODES: Oh, I am so glad you asked. I am a ratings and revenue queen. Number 1 or 2 in the ratings usually. So what are the "mainstream" talking about? Well, they say Liberals don't make money because no one wants to hear them. Okay, let's think.

...
BUZZFLASH: Explain the allegations that Rush Limbaugh has stated, that if Clear Channel syndicated your show, he would take his program to another company. Could there be a Democratic or Progressive Rush Limbaugh type personality on the airwaves?

RHODES: Not at Clear Channel.

First, let me tell you where the story came from. I had two meetings with middle managers who both liked me and what I had done for our 'pod'. (At Clear Channel the territories are split up into 'pods'.) In two separate meetings I was told "The Rush story." Additionally, I should never expect to be syndicated by Clear Channel because Rush had said he'd just do what advertisers do. He'd go somewhere else. I was an unknown, he was a known.

Another oft-repeated conservative meme reputed by someone who'd know. It's not surprising, though; there's a marked tendency among a lot of "free-market advocates" to try to defend actions by companies in an imperfect market using arguments that would only work in a perfect one. Radio is an imperfect market because of the limited number of wavelengths available and the relative permanence of ownership of those wavelengths, and it lends itself well to concentration. Thus you get kingmaking groups like Clear Channel.

(The way to get around this, of course, is to make talk radio obsolete. Great idea, but it ain't gonna happen anytime soon. Digital radio isn't that popular.)