How Powerful are Political Parties in Shaping Public Opinion? Evidence from Two Quasi-Experiments

How powerful are political parties in shaping citizens’ opinions? Political scientists have long wrestled with this question, yet most existing research faces one inherent obstacle: In order to gain credible exogenous variation in party cues, scholars are usually forced to study partisan elite influence on peripheral issues far from the center of party competition. We study partisan elite influence during a period where sharp — and unexpected — variation in party position–taking occurred on two major and highly salient policy issues. Using these two events as quasi-experiments, we analyze media content and data from a fivewave panel survey of public opinion collected in Denmark in 2010-11 to demonstrate the magnitude of partisan leadership of opinion. Our findings show that citizens’ policy opinions are indeed responsive to cues from their party, and the effects are enduring over time. Strikingly, party cue effects appear homogeneous across a large range of individual-level characteristics.