Three-round presidential elections: the effects of open, simultaneous, and mandatory primaries in Argentina and Uruguay

Abstract This article analyses primary presidential elections – open, simultaneous and mandatory for political parties – in Uruguay and Argentina. In spite of their similarity, both systems have some differences: i) voting is mandatory in Argentina and voluntary in Uruguay; ii) in Argentina, the presidential candidate must run in the primary along with a vice presidential candidate, while in Uruguay the primary solely decides the presidential candidate. Through a neo-institutionalist approach and the primary electoral results, the present research shows that different rules cause significantly different outcomes. Primaries in Uruguay promote internal contestation and a diversity of alternatives within and among parties. In Argentina, the system discourages competition and stimulates elite coordination from the beginning of the process, concentrates the candidate supply, and organizes preferences into two main blocks.