The relevance and importance of research for understanding policy processes and influencing policies has been much debated, but studies on the effectiveness of policy theories for predicting and informing opportunities for policy change (i.e. prospective policy analysis) are rare. The case study presented in this paper is drawn from a policy analysis of a contemporary process of policy debate on legalization of abortion in Indonesia, which was in flux at the time of the research and provided a unique opportunity for prospective analysis. Applying a combination of policy analysis theories, this case study provides an analysis of processes, power and relationships between actors involved in the amendment of the Health Law in Indonesia. It uses a series of practical stakeholder mapping tools to identify power relations between key actors and what strategic approaches should be employed to manage these to enhance the possibility of policy change. The findings show how the moves to legalize abortion have been supported or constrained according to the balance of political and religious powers operating in a macro-political context defined increasingly by a polarized Islamic-authoritarian-Western-liberal agenda. The issue of reproductive health constituted a battlefield where these two ideologies met and the debate on the current health law amendment became a contest, which still continues, for the larger future of Indonesia. The findings confirm the utility of policy analysis theories and stakeholder mapping tools for predicting the likelihood of policy change and informing the strategic approaches for achieving such change. They also highlight opportunities and dilemmas in prospective policy analysis and raise questions about whether research on policy processes and actors can or should be used to inform, or even influence, policies in 'real-time'.