Although ideological polarization creates problems in terms of governability and even for democratic stability, I argue that it has positive effects in new democracies because it contributes to the formation of party systems that are responsive to voter preferences. This contention is supported by a comparative historical analysis of ten Latin American cases showing that the vast differences in party system responsiveness across the continent are rooted in the historical balance of power between the left and right, which, in turn, leads to a bifurcation of Latin American party systems in the first half of the 20th century. While prolonged periods of ideological conflict occurred in some countries, polarization was aborted in others. No matter whether party cartels were formed by conservative actors, or by revolutionary parties of the left that swept the political landscape, party systems that followed the second route share the lack of responsiveness to voter preferences and a rampant use of clientelism in voter mobilization. An analysis of the quality of representation using data from the 1980s and 1990s demonstrates that how political actors responded to ideological polarization in the first half of the 20th century continued to shape party system responsiveness after the most recent wave of re-democratization.