Jim A. Kuypers’ recent book, Press Bias and Politics, has made a significant advance in the methodology of inquiring into this issue—although it’s a safe bet that many in the scholarly community will be tempted to dismiss it out of hand. That’s a shame, if so, because even if one is disinclined to accept Kuypers’ conclusion that the press tends to favor ideas associated with the political left, his method can at least put the debate on a firmer footing.
Cooper, S. D. (2005). Bringing some clarity to the media bias debate. Review of Communication, 5, 81-84.