Carlos Diaz-Rosillo is a Ph.D. candidate in Government at Harvard University. Carlos studies chief executive power in the United States and examines the different types of instruments, or power tools, that chief executives have at their disposal to exert leadership and achieve policy outcomes. Taking the American presidency as a starting point, his research seeks to increase our understanding of how chief executives, working in systems where separate institutions share, check and compete for power, are able to affect policy and provide leadership as the energizing elements of our governments. It hopes to provide a model to explain when American presidents will choose a particular weapon in their arsenal of powers to achieve a desired outcome, the specific factors that trigger those choices, and their effect. In addition to increasing our understanding of presidential power, his research hopes to illuminate scholarship on the exercise of leadership by different chief executive officers, both in the public as well as the private sector.