This article examines social cleavages and the impact of political legacies on Chile's post-authoritarian party system. In contrast to society-oriented approaches to party system formation, we argue that cleavage appearance in a party system depends on political agency, which can even (re)create social identities and social conflicts. The Chilean case illustrates this point; the structure of the party system is deeply influenced by distinctive political legacies of the authoritarian period. The cleavage between those who supported authoritarian rule and those who opposed it has powerfully shaped the party system during the new democratic period.

In post-authoritarian Chile (1990–2001), a societal approach does not adequately explain the formation of cleavages or the contours of the party system. A class cleavage has appeared between the governing coalition and the conservative opposition, but this cleavage is politically constructed and maintained. The Chilean case also shows that it is important to examine the ways in which political elites craft party systems from above during the transition period. Political agency from the supply side played a decisive role in emphasizing or diminishing some of the political and cultural conflicts existing after the authoritarian experience and, therefore, an essential role in party system formation in post-authoritarian Chile.