Charter schools have moved from being widely viewed as a marginal force in public education reform to taking on a central role in our national, state, and local debates around improving education. And a growing number of policymakers--including superintendents, mayors, governors, and even U.S. Secretary of Education Arne Duncan--are using chartering as a critical tool to drive school improvement and meet the needs of underserved children. These developments create new demands on authorizers to strategically manage their portfolios by effectively monitoring the quality of the schools they have chartered, closing low-performing schools, and fostering the replication and growth to scale of high performers. Charter school authorizers are under increasing pressure--from policymakers, funders, and the media--to assume a variety of responsibilities, including spurring struggling and mediocre schools to higher levels of achievement, attracting high-quality operators, and fostering the replication of successful schools--in addition to their more established roles of approving charter applications, monitoring school performance, and closing low-performers. Key questions for authorizers--and the charter school movement more generally--are which of these roles are really appropriate for authorizers to take on, which they can reasonably be expected to do well, and which would be better addressed by other entities, including those that do not yet exist. This paper, created as part of the National Association of Charter School Authorizers' (NACSA's) federally funded Performance Management, Replication, and Closure (PMRC) project to improve the policies and practices of authorizers in these key areas, looks at how a set of seven leading authorizers (herein called "model authorizers")--all of whom oversee substantial numbers of schools, have been authorizers for some time, and are nationally regarded as leaders in the field--are responding to new challenges and demands in the three areas where expectations for authorizer performance are undergoing the greatest evolution: performance management, replication, and closure. The author finds that even the most forward-looking authorizers are struggling to develop effective policies and practices in these areas, and no one authorizer has "all the answers." At the same time, the author finds that authorizers are highly cognizant of the complex implications of the new roles that charter schools are being asked to play in public education reform, and are creating new practices, processes, and tools to address some of those implications. Every one of the seven authorizers is currently taking steps to refine, improve, or create new practices in these three key areas. These examples show that the most effective authorizers are learning from experience and data, and steadily working to improve the quality of their practices, processes, and policies. (Contains 2 figures.)