On my To Do list - save this link and track down reactions.
A Measure of Media Bias
Department of Political Science, UCLA, and
Graduate School of Business, Stanford University
Harris School of Public Policy
University of Chicago
UPDATE: Hmm, a substantive objection to the methodology appears in the comments. Oh, enough with the false modesty:
...the media may cite a think tank merely because a Congresssperson did; if (in the current situation) Reps are being cited based on, for example, Treasury Dept studies, and Dems are rebutting with think-tank studies, a truly "fair and balanced" story presenting both sides may score as biased. That methodological flaw would shift in an era when Dems controlled the Gov't. (Heaven forbid).
As an example (illustrative, but hardly probative), the NY Times cites the (liberal) Economic Policy Institute in this story on Kerry's minimum wage proposal. The EPI quote balances a quote from the Bush campaign, and is from one of the authors of Kerry's proposal (Kerry's experts need to keep their day jobs, for now). If I grasp the methodology of the study, this story scores as tilted left, but is it really?