This book explores the origins of presidential powers in new constitutions. Much is known about the effects of different presidential powers—less on the conditions that lead to their emergence. The book focuses on the origins of these powers. It argues that the most important predictor of whether a new constitution will expand (instead of restrict) presidential powers is power asymmetry, or more specifically, the difference in power assets between the Incumbent and the Opposition. These power assets can include electoral results, seats at key institutions such as the negotiating table, and even approval ratings. This argument draws from bargaining theories on self-dealing. Power asymmetry is a more powerful variable in explaining variations in presidential powers than others, such as the president’s ideology, class differences, or overall economic conditions. To make the case for this argument, the book reviews all the constituent assemblies from Latin America since the late 1980s, as well as several failed assemblies, and thereby provides one of the most comprehensive reviews of constitutional overhaul in Latin America thus far. The book also examines constitutional amendments that affect presidential powers, especially term limits. The conclusion is that to get more balanced constitutions (i.e., those that strengthen checks on presidential powers), neither side of the debate should have a huge power advantage over the other.