1. Introduction Juan Pablo Luna, Rafael Piñeiro Rodríguez, Fernando Rosenblatt and Gabriel Vommaro; 2. The Case of Uruguay's Frente Amplio Verónica Pérez Bentancur, Rafael Piñeiro Rodríguez and Fernando Rosenblatt; 3. Horizontal coordination and vertical aggregation mechanisms of the PRO in Argentina and its subnational variations Gabriel Vommaro; 4. Bolivia's Movement Toward Socialism (MAS): A Political Party Based on and Anchored in Social Movements Santiago Anria; 5. The complex interaction between vertical interest aggregation and horizontal coordination: The PRD and MORENA in Mexico Hélène Combes; 6. PLN and PAC: Two Costa Rican parties with evolving constituencies in opposite directions Ronald Alfaro-Redondo and Steffan Gómez-Campos; 7. The Case of the Traditional Parties in Paraguay Diego Abente Brun; 8. The Colombian Liberal Party and Conservative Party: From Political Parties to Diminished Subtypes Laura Wills-Otero, Bibiana Ortega and Viviana Sarmiento; 9. 'Normal' Parties in Extraordinary Times: The Case of Primero Justicia and Voluntad Popular in Venezuela Jennifer Cyr; 10. Diminished by Design: Ecuador's Alianza PAIS Catherine M. Conaghan; 11. The Chilean PPD: A Loose Confederation of Leaders Rafael Piñeiro Rodríguez, Fernando Rosenblatt and Sergio Toro Maureira; 12. Fujimorismo and the Limits of Democratic Representation in Peru Alberto Vergara and María Claudia Augusto; 13. The Unidad Nacional de la Esperanza: Guatemala's Only True Political Party? Omar Sanchez-Sibony and Jonatán Lemus; 14. Conclusions Juan Pablo Luna, Rafael Piñeiro Rodríguez, Fernando Rosenblatt and Gabriel Vommaro.