Purpose: Drawing upon research into standards reform, and theorizing of professional and political capital, this article seeks to understand the development of and advocacy for the Next Generation Science Standards in the United States. As well as revealing how professional capital exists in three dimensions--human, social, and decisional--the research argues professional capital also needs to be understood as inherently political. Research Methods/Approach: The research draws upon interviews and discussions with key educators who developed and supported the Next Generation Science Standards at state and national levels. Findings: The article reveals political capital as vital for promoting educational standards reform, managing perceptions of reform, and making pragmatic decisions to ground reform in context. Political capital is a complex, contingent capacity vital to the development and acceptance of science education reform. Implications: Findings have implications for understanding power dynamics that characterize reform in schooling systems and professional contexts more broadly.