Campaign promises are a cornerstone of representative democracy. Candidates make promises to signal to voters their intentions in office and voters evaluate candidates based on those promises. This study unpacks the theorized pathway regarding campaign promises: not whether promises are kept, but what purpose promises serve, what they signal, and how they affect voter decision-making. The author explores the pathways and conditions influencing promises and finds that promises tend to have a polarizing effect on voters' opinions of politicians, attracting similarly-positioned voters and strongly repelling voters who disagree with a candidate's position. In addition, voters perceive promise breakers as less honest and less likely to follow through than candidates who more weakly took the same position. With a wealth of data and fascinating case studies, this book is full of important insights into electoral psychology and the study of promises, campaigning, and representation.