How do partisan media affect polarization and partisanship? The rise of Fox News, MSNBC, and hyper-partisan outlets online gives this question fresh salience, but in this paper, we argue that the question is actually not new: prior to the broadcast era, newspapers dominated American mass communication. Many of these were identified as supporting one party over the other in their news coverage. While scholars have studied the composition and impact of the partisan press during their 19th-century height, the political impact of the gradual decline of these partisan papers remains relatively under-examined. The unnoted vitality and endurance of partisan newspapers (which constituted a majority of American newspapers until the 1960s) represents a huge hole in our understanding of how parties communicate. As a consequence of this omission, scholars have ignored a potentially vital contributing factor to changing patterns of partisan voting. In this paper, we examine both the degree and influence of partisanship in historical newspapers. We begin by content analyzing news coverage in the Los Angeles Times from 1885-1986 and the Atlanta Constitution from 1869-1945. To avoid problems of selection bias and the absence of a neutral baseline of coverage in the coded news, we focus on a subset of partisan news for which we have access to neutral coverage of a full population of potential stories: the obituaries of U.S. Senators. By coding whether and how the papers covered the deaths of these partisans over time, we are able to systematically test for bias. We then collect information on newspaper editorial stances from Editor and Publisher’s Annual Yearbook to examine the impact of newspaper partisanship on voting patterns in presidential elections from 1932-92. Specifically, we test whether the proportion of partisan news outlets in a given media market explains changes in the rate of polarized voting.
Groeling, Tim, and Matthew Baum. "Partisan News Before Fox: Newspaper Partisanship and Partisan Polarization, 1881- 1972." HKS Faculty Research Working Paper Series RWP13-035, September 2013.