This book challenges the approach of relying on election outcomes to analyse party systems, contending that changes can be also identified and documented beyond the scope of parliamentary elections through legislative party switching. It argues that significant party system changes occur often within parliamentary terms, and legislative party switching is not a pathological feature of democracy but rather an integral component of democratic party systems. Offering a comprehensive and specific theoretical framework for party switching and based on a novel and exhaustive database from Czech Republic, Lithuania, and Poland, this book examines the determinants for, and implications of, legislative party switching in Central and Eastern Europe. This book will be of key interest to scholars and students of legislative studies, party politics, Central and East European politics, and more broadly comparative politics and government. The Open Access version of this book, available at www.taylorfrancis.com, has been made available under a Creative Commons Attribution-Non Commercial-No Derivatives (CC-BY-NC-ND) 4.0 license. Any third party material in this book is not included in the OA Creative Commons license, unless indicated otherwise in a credit line to the material. Please direct any permissions enquiries to the original rightsholder.