Background/Context: The concept of scale has gained purchase across social sectors in recent years as organizational leaders and funders seek to maximize the impact of promising social innovations. Purpose/Objective: We apply insights from recent scholarship on ideas as mechanisms for change to explain how the idea of "getting to scale" intersected with political opportunities and human and financial resources in the early diffusion of the charter management organization (CMO). Research Design: As the birthplace and a political locus of the CMO form, California is an ideal vantage point from which to understand the early years of the form's diffusion. We conducted interviews with California CMO and non-CMO leaders, principals, and funders. Our interviews were designed to understand when and why CMO leaders thought about growth, the challenges and opportunities associated with growth, organizational goals and strategic priorities, and whether and how funders shaped CMO development and plans. In addition, we constructed a school-level panel dataset for the 1991-92 to 2006-07 school years using data from the National Center for Education Statistics Common Core of Data and the California Department of Education. We included charter organizational form, enrollment, and school founding and closure years. We also joined multiple Foundation Center datasets to create a grant-level dataset for the years 1999 to 2006 that includes grant amount, grant type, recipient, and funder. Finally, we conducted participant and nonparticipant observations at CMO board meetings, foundation staff meetings and presentations, and charter school conferences and meetings. Findings/Results: Understood and framed as the vehicle for getting to scale, the CMO form drew a disproportionate share of private philanthropy dollars, appealed to a new class of professionals from outside of education, and was successfully distinguished from alternative charter forms, all of which contributed to its early diffusion. Conclusions/Recommendations: We develop a fuller understanding of the charter school movement, describing how the diffusion of the CMO form displaced ideas about school-level autonomy and decentralization in favor of ideas about getting to scale and tipping the system. The study also offers insight to scholars analyzing current and past efforts at educational reform by emphasizing the roles played by ideas, opportunities, and resources.