Why Should the Republicans Pray for Rain? Electoral Consequences of Rainfall Revisited

Existing studies—most importantly, Gomez, Hansford, and Krause—provide empirical support for an idea often embraced by popular media: The vote share of the Republican Party (as the percentage of total votes) increases when it rains, because the magnitude of decrease in turnout is larger among Democratic vis-à-vis Republican supporters. Considering the compositional nature of aggregated data, we show that the alleged Republican advantage derives in part from an increase in the number of votes for the Republican Party. Based on the extensive literature of psychology and related fields, we provide a possible interpretation of this counter-intuitive empirical finding. Methodologically, our evidence suggests that researchers must be alert when using rainfall as an instrument to estimate the causal effects of voter turnout on electoral outcome.