Tyler Cowen points to an article by Riccardo Puglisi, who writes:
Controlling for the activity of the incumbent president and the U.S. Congress across issues, I find that during a presidential campaign, The New York Times gives more emphasis to topics on which the Democratic party is perceived as more competent (civil rights, health care, labor and social welfare) when the incumbent president is a Republican. This is consistent with the hypothesis that The New York Times has a Democratic partisanship, with some “anti-incumbent” aspects . . . consistent with The New York Times departing from demand-driven news coverage.
I haven’t read the article in the question but the claim seems plausible to me. I’ve often thought there is an asymmetry in media bias, with Democratic reporters–a survey a few years ago found that twice as many journalists identify as Democrats than as Republicans–biasing their reporting by choosing which topics to focus on, and Republican news organizations (notably Fox News and other Murdoch organizations) biasing in the other direction by flat-out attacks.
I’ve never been clear on which sort of bias is more effective. On one hand, Fox can create a media buzz out of nothing at all; on the other hand, perhaps there’s something more insidious about objective news organizations indirectly creating bias by their choice of what to report.
But I’ve long thought that this asymmetry should inform how media bias is studied. It can’t be a simple matter of counting stories or references to experts and saying that Fox is more biased or the Washington Post is more biases or whatever. Some of the previous studies in this area are interesting but to me don’t get at either of the fundamental sorts of bias mentioned above. You have to look for bias in different ways to capture these multiple dimensions. Based on the abstract quoted above, Puglisi may be on to something, maybe this could be a useful start to getting to the big picture.