J. Lat. Amer. Stud., Page of © Cambridge University Press doi:./SX Why New Parties Split: The Schism of Peru’s United Left in Comparative Perspective BRANDON VAN DYCK* Abstract. Why do new parties split? Scholars of new party schisms shy away from leadership-centred explanations for fear of excessive voluntarism and thus fail to con- ceptualise differences between leaders systematically. This article challenges that trend, arguing that externally appealing, internally dominant leaders generate cohesion in new parties. It analyses why some externally appealing leaders are internally dominant, while others are not, and argues that this variation can make the difference between schism and survival. The article supports its argument through a representative case study: the fatal (and consequential) schism of Peru’s United Left coalition in the late s. Keywords: political parties, Latin America, cohesion, leadership, theory construction Introduction The vast majority of new political parties die. Nevertheless, existing scholar- ship largely ignores unsuccessful cases of party-building and focuses on the small number of success stories. This selection on the dependent variable is Brandon Van Dyck is Assistant Professor of Government and Law at Lafayette College. Email:
[email protected] * The author would like to acknowledge Harvard’s David Rockefeller Center for Latin American Studies, whose generous research grant made the fieldwork for this article possible. Henry Hale, Why Not Parties in Russia? Democracy, Federalism, and the State (Cambridge: Cambridge University Press, ). Thomas Mustillo, ‘Modeling New Party Performance: A Conceptual and Methodological Approach for Volatile Party Systems’, Political Analysis, : (), pp. –. Steven Levitsky, James Loxton and Brandon Van Dyck, ‘Introduction: Challenges of Party-Building in Latin America’, in Steven Levitsky, James Loxton, Brandon Van Dyck and Jorge Domínguez (eds.), Challenges of Party-Building in Latin America (New York: Cambridge University Press, ), pp.