"In recent years, political scientists and journalists have taken a great interest in the question of whether the American electorate is "sorting" into communities based on partisan affiliation. That is, there is concern that American communities are becoming increasingly politically homogenous and this is because Americans are considering politics explicitly when determining where to live. Academics have since debated the degree to which this is a real phenomenon and, if it is, whether it has important normative implications. However, little empirical research has examined which factors turned some closely-contested counties into Republican enclaves and others into Democratic strongholds. Examining individual and aggregate data and employing a large number of statistical methods, George Hawley explores the increasing political homogenization of small geographic units and explains the causal mechanisms driving this phenomenon as well as its consequences for individual pol