"This book is the most comprehensive study to date about the consequences of campaigns using "microtargeting" databases to mobilize voters in elections. In spite of the popular aura of campaigns using secretive and sophisticated techniques to engage with voters, the book shows that most of what campaigns know about voters comes from a core set of public records. States vary in the kinds of records they collect from voters. Sometimes, state legislators pass laws about data collection for the very purpose of using government-collected personal data for their campaigns. The variation in data across the country means that campaign databases look different in different areas. Consequently, campaigns vary how they engage with voters in different areas because of the data that permit them to perceive voters' interests. Variations in data policy thus affect the kinds of electoral coalitions that campaigns build"--