Since democratization, political parties in Argentina and Chile have pursued different policy strategies to win the support of voters, with party switching characterizing the former and policy stability in the latter. Our framework proposes that such policy differences are closely related to the constraints and opportunities that are provided by non-policy endowments. Here, we describe the effect of non-policy endowments on the parties’ ability to switch their prior policy positions using our model to define the optimal policy offer that parties should make given their non-policy advantages or disadvantages as well as the presence of non-policy heterogeneity among voters’ preferences. In so doing, we describe biases in policy responsiveness derived from the different sensitivity of richer or poorer voters to policy and non-policy offers by parties in either country. We end by discussing whether non-policy incentives shape the observable strategies of politicians in Argentina and Chile and how they may differ from their optimal choices, as well as the implications of our analysis for the subsequent political evolution of parties in both countries.