How do changes in electoral rules affect the nature of public policy outcomes? The current evidence supporting institutional theories that answer this question stems almost entirely from quantitative cross-country studies, the data of which contain very little within-unit variation. Indeed, while there are many country-level accounts of how changes in electoral rules affect such phenomena as the number of parties or voter turnout, there are few studies of how electoral reform affects public policy outcomes. This article contributes to this latter endeavor by providing a detailed analysis of electoral reform and the public policy process in Thailand through an examination of the 1997 electoral reforms. Specifically, the author examines four aspects of policy-making: policy formulation, policy platforms, policy content, and policy outcomes. The article finds that candidates in the pre-1997 era campaigned on broad, generic platforms; parties had no independent means of technical policy expertise; the government targeted health resources to narrow geographic areas; and health was underprovided in Thai society. Conversely, candidates in the post-1997 era relied more on a strong, detailed national health policy; parties created mechanisms to formulate health policy independently; the government allocated health resources broadly to the entire nation through the introduction of a universal health care system, and health outcomes improved. The author attributes these changes in the policy process to the 1997 electoral reform, which increased both constituency breadth (the proportion of the population to which politicians were accountable) and majoritarianism.