One Bias Fits All? Three Types of Media Bias and Their Effects on Party Preferences

Bias in political news coverage may have a profound influence on voter opinions and preferences. However, the concept of media bias actually encompasses different sub-types: Visibility bias is the salience of political actors, tonality bias the evaluation of these actors, and agenda bias the extent to which parties address preferred issues in media coverage. The present study is the first to explore how each type of bias influences party preferences. Using data from the Austrian parliamentary election campaign of 2013, we combine an online panel survey (n = 1,285) with measures of media bias from content analyses of party press releases (n = 1,922) and media coverage in eight newspapers (n = 6,970). We find substantial effects on party preferences for tonality bias and agenda bias, while visibility bias has no clear impact. Voters who are less politically sophisticated and lack a party identification are more susceptible to bias, and media bias can also reinforce existing partisan identities.