Persistence of Political Partisanship: Evidence from 9/11

This paper empirically examines whether the act of deciding to support a political party can impact partisan leanings years later. We use the discontinuity in the probability of being registered to vote around the 18th birthday to look at the impact of registration after the 9/11/01 attacks on party of registration. We rst show that 9/11 increased Republican registration by approximately 2%. Surprisingly, these di¤erences in registration patterns fully persist over the two year period from 2006 to 2008, even for a group of registrants who moved and changed their registration address. We nd full persistence for those registered in zip codes within two miles of a four year university, suggesting that persistence is unlikely to be explained by lack of easy access to or inability to process information. Instead, we suggest an interpretation of our ndings based upon either cognitive or social biases.