The two-party system has long characterized American politics, but partisanship as it is understood today is a relatively recent phenomenon. Today, partisanship is not simply based on one's voting record but a totalizing sense of identification with one party over the other. Consequently, the American political climate is more polarized than ever before. Though this fact is often reported with alarm, it may be too soon to determine whether partisanship actually damages democracy. This volume examines what partisanship means today, how this differs from historical partisanship, its contributing factors, and the effect it has on the country.