Mass media and political polarization in the United States

This dissertation is composed of three papers broadly examining the relationship between the mass media and political polarization in the United States. The first paper examines whether the media might have played a role in the polarization of the American public. Using an automated content analysis of almost 600,000 news articles and transcripts from a variety of prominent news media sources over the past four decades, the paper analyzes whether coverage of ten issues has changed over time along several dimensions of tone (affect, incivility, conflict) and source cues (in particular, whether the media cover increasingly more extreme politicians). The results indicate that the media likely contributed to the process of partisan sorting by increasingly providing the public with partisan signals in the news coverage. There is also some evidence that the media contributed to the affective polarization of the public. The second paper focuses on the nature of media coverage of climate change and its effect on public opinion polarization of climate change attitudes, finding that despite the common perception, the media, including conservative media, did not overwhelmingly promote climate change skeptics, industry groups, or denialist organizations. Instead, the coverage featured an increasing number of partisan cues as the issue rose in salience, which polarized the public. In the third paper, I examine the relationship between climate change attitudes and news media diets. Previous work has focused extensively on Fox News and posits that Fox has been a dominant player in turning the Americans, and especially Republicans, into climate skeptics. Utilizing a large national survey, I find that the relationship is more nuanced than previously argued. Fox News does seem to have a negative effect on supporting governmental action in reducing greenhouse gas emissions, though that effect is limited to a small group of purists stuck in the conservative echo chamber. Most people, and importantly, most Republicans, are not very likely to be members of that group.