Abstract
<jats:title>Abstract</jats:title> <jats:p>National leaders worldwide are eroding democracy, yet it remains unclear which ones are most likely to undermine democratic institutions and norms. This book integrates differential psychology research with comparative politics to propose a theory about the conditions in which the individual differences among presidents have a measurable impact on executive governance. To test the theory, the author developed the Presidential Database of the Americas (PDA), a unique database that contains biographical and psychometric data on Western Hemisphere presidents since 1945. A total of 688 experts on presidents produced 903 evaluations for 228 Western Hemisphere leaders who governed between 1945 and 2021. Drawing on semi-structured interviews with 24 former presidents from ten countries, the author conducts a comprehensive analysis of Latin American presidential constitutional power grabs between 1945 and 2021, when 14% of the rulers attempted to extend their term limits or expand their powers. These power grabs have been commonplace across regimes, countries, and historical periods, and the list of perpetrators includes some of the most influential leaders of the previous and the current century, who have dramatically changed the course of their countries. Statistical analyses reveal that dominant and politically inexperienced presidents are more likely to attempt to relax their term limits, while risk-taking and assertive leaders are more inclined to expand their formal powers. These efforts, in turn, have eroded democracy across the region. By treating political leaders’ traits as independent variables, this book offers new insights into the study of democracy, elites, institutions, and the presidency.</jats:p>