Political advertising plays a key role in modern electioneering and has formed part of political campaigns since the earliest federal elections were held in the United States. As modes of mass communication have evolved, so have the venues for campaign advertising—from newspapers to radio and television, and today, the Internet. Not only have the outlets for political advertising expanded over the past twenty years, so have the number of groups using it to convey information and advance their points of view. Because political advertising has become such a pervasive medium for candidates, political parties, and special interest groups, understanding its role in election campaigns becomes all the more important. Crowded Airwaves gathers some of the most significant new work in American political advertising and communication. The contributors provide an objective and balanced analysis of political advertising: its causes, its growth, and its consequences on elections in the United States. The chapters in this volume tackle three of the most interesting and most complicated issues in political advertising today: the characterization of ads and the need to measure their impact; the agenda-setting and priming effects of ads; and the role and implications of issue advertising for the electorate. The contributors focus in particular on the effects and consequences of negative advertising. Crowded Airwaves will appeal to readers who are interested in political campaigns and communication. It will be of special importance to those concerned with the tone and content of electoral campaigns and political discourse.