The Persuasive Effects of Direct Mail: A Regression Discontinuity Based Approach

During the contest for Kansas attorney general in 2006, an organization sent out six pieces of mail criticizing the incumbent’s conduct in office. We exploit a discontinuity in the rule used to select which households received the mailings to identify the causal effect of mail on vote choice and voter turnout. We find these mailings had a politically significant effect on the challenger’s vote share, which is statistically significant in most, but not all, of our specifications. Our point estimates suggest that a 10 percentage point increase in the amount of mail sent to a precinct increased the challenger’s vote share by 1.5 to 3.5 percentage points. Furthermore, our results suggest that these mailings had little mobilizing effect, suggesting that the mechanism for this increase was persuasion.