Why do advocacy campaigns succeed in some cases but fail in others? What conditions motivate states to accept commitments championed by principled advocacy movements? Joshua W. Busby sheds light on these core questions through an investigation of four cases - developing-country debt relief, climate change, AIDS, and the International Criminal Court - in the G-7 advanced industrialized countries (Canada, France, Germany, Italy, Japan, the United Kingdom, and the United States). Drawing on hundreds of interviews with policy practitioners, he employs qualitative, comparative case study methods, including process-tracing and typologies, and develops a framing/gatekeepers argument, emphasizing the ways in which advocacy campaigns use rhetoric to tap into the main cultural currents in the countries where they operate. Busby argues that when values and costs potentially pull in opposing directions, values will win if domestic gatekeepers who are able to block policy change believe that the values at stake are sufficiently important.