The Variable Persuasiveness of Political Rhetoric

Which types of political rhetoric are most persuasive? Politicians make arguments that share common rhetorical elements, including metaphor, ad hominem attacks, appeals to expertise, moral appeals, and many others. However, political arguments are also highly multidimensional, making it difficult to assess the relative persuasive power of these elements. We report on a novel experimental design which assesses the relative persuasiveness of a large number of arguments that deploy a set of rhetorical elements to argue for and against proposals across a range of UK political issues. We find modest differences in the average effectiveness of rhetorical elements shared by many arguments, but also large variation in the persuasiveness of arguments of the same rhetorical type across issues. In addition to revealing that some argument-types are more effective than others in shaping public opinion, these results have important implications for the interpretation of survey-experimental studies in the field of political communication.