Why Don’t States Switch Sides Anymore? The Rise and Fall of American Electoral Volatility

American electoral volatility is in a free fall. Overtime variation in the partisan balance of presidential elections across states has matched an all-time low in American history and is a fraction of its 1970’s peak. The current decline in volatility parallels declines during the Gilded Age and Franklin Roosevelt’s presidency. Trends in electoral volatility vary regionally, and the South’s patterns of electoral volatility are distinctive. This paper develops a theory of electoral volatility at the voter level based on the premise that volatility is due to voter uncertainty. Party polarization makes the parties’ positions distinct and reduces volatility. Close elections increase incentives for voters to become informed and for campaigns to inform voters, which reduce voter uncertainty. Increased voter turnout and a larger number of votes cast per state also decrease volatility. The model is empirically validated using both historical aggregate data from 1832 to 2012 and American National Election Studies (ANES) data at the voter level from 1952 to 2012.