With my paper I introduce a new tool to measure presidential power: the index of constitutional presidential strength (CPS). This index places emphasis on the president as a significant player in non-presidential systems. Established measurement tools are quickly stretched to their limits if they are to account for both semi-presidential and parliamentary systems. Part 1 the paper will therefore discuss the established measurement tools, especially criticizing how well-grounded, in terms of theory and methodology, they are. Part 2 will introduce the new measurement tool, which is especially useful to measure low-level constitutional competences and proposes a balance of content and concept validity. With this proposed balance and the possibility for researchers to decide which data to use, the index of CPS offers methodologically and empirically sound paths for further research. Furthermore, the application in 46 countries over 70 years provides a comprehensive data collection for presidential strength.
