The Electoral College can misfire, electing a president who loses the popular vote (as in 2000 and 2016), but the presidential nomination process can misfire as well, producing a nominee (as in 1952 or, more recently, 2016) who is less popular among party voters than other candidates in the party. The cause of this is the byzantine web of state laws and party rules governing the process. This book explores those rules, enabling us to make sense of the process and understand how presidential candidates have been selected throughout American history. Surprisingly, for much of American history, the major party’s nominees were chosen by party leaders, not ordinary voters, and even today, the process is far less democratic than many imagine. Not every voter is able to participate in the process, and not every vote is weighted equally. This book examines the evolution of the rules governing the nomination process and how those rules contribute to the increasing ideological polarization of our politics today.