In this book, Josep M. Colomer argues, against much conventional wisdom, that political polarization is embedded in the constitutional design. The book puts forth that sustained conflict and institutional gridlock are not mainly questions of character, personalities, or determined by socioeconomic or cultural inequalities. They are, above all, the result of the formula of separation of powers between the Presidency and Congress, which, together with a system of only two parties, fosters adversarial politics and polarization. Colomer contends that in the past, bipartisan cooperation and domestic peace flourished only under a foreign existential threat, such as during the Cold War. Once such a threat vanished, unsettled issues and new social concerns have broadened the public agenda and triggered again animosity and conflict. Constitutional Polarization offers innovative and relevant insights in political science to a broad readership without technical or academic jargon. It will be of high interest for those reader attentive to current affairs, as well as for public officers, journalists, pundits, and those in the study of political science, where it can also become a staple for courses in American Politics.