Indeed, the findings of the MRC when blended with numberg's own study implies something quite different, as this paragraph shows:
In Boyd's survey, conservative politicians were mentioned overall more than two-and-a-half times as frequently as liberals, which was pretty much what I found in my study. And my study and others have showed that groups like the Heritage Foundation are mentioned four times as frequently as liberal groups like the ADA. By failing to correct for these differences, the MRC study stacked the deck -- it turns a discrepancy in the overall number of mentions of liberal and conservative politicians into a specious discrepancy in the frequency with which they are labeled. Once again, the press are being charged with a liberal bias because they mention liberals less than they do conservatives.
So, conservative politicians get mentioned more often. That would imply that they're quoted more often, listened to more often, their ideas are discussed more often... (which the flap over the 9th circuit ruling would seem to imply...)
funny, that doesn't really sound much like liberal bias to me. If it is, it's the kind of liberal bias that some who understands the old dictum that "there's no such thing as bad publicity" would kill for would kill for. A debunked or disputed idea is only as weak as the degree to which people believe its opponents, whereas an ignored idea is powerless.