This course explores the origins, purposes, roles, and consequences of political parties in the American political system. After a brief consideration of the broader theories behind political party systems, we will turn our focus to the party system in the United States. V. O. Key (1964) presented a tripartite definition of political parties that we will use to structure our exploration of parties for the rest of the course: party as organization, party in government, and party in the electorate. In these sections, we will address political party polarization, party identification, parties' fundraising, and many other related topics. From this rich examination of political parties in the U.S. context, we will discuss why parties exist and enable democracy, but also discuss their potential flaws and failures.