We have acquired, over the last several decades, a fairly rich understanding of the impact on voter behavior of political communication in general and of political advertising specifically. Yet much of this knowledge pertains to “traditional,” candidate-centered elections; comparatively very little is known with regards to ballot initiative races. In principle, these contests pit not people, but proposed policies, against each other. In practice, however, they not only feature ads discussing policy, but also frequently comprise ads highlighting a measure’s supporters and opponents, be they individuals, non-profit groups, media outlets, industries, or political parties. This, in turn, leads to a basic query: what types of advertising message carry the greatest weight with voters in initiative contests – and how do they differ (if at all) from the effects they have in similar ads run in candidate-centered elections? Through an original experiment, this dissertation aims to break new ground in the voter behavior, media effects, and direct democracy literature by tackling this question. / Political Science