This chapter presents our explanatory framework and introduces a statistical model of vote choice, with individual-level variation on policy offers and non-policy endowments. In our framework, voters assess the non-policy endowments of parties and their policy offers. Heterogeneity in the weight that voters attach to benefits results in some groups of voters providing larger electoral returns to parties. Therefore, responsiveness should be biased toward those voters that feel more intensely about distinct policy and non-policy benefits in the portfolio of parties. Furthermore, our model shows that parties with a comparative non-policy advantage will benefit from taking policy positions that are closer to the median voter whereas parties lacking such advantage should advertise more extreme policy offers. As parties are constrained by their different non-policy endowments, they will deliver different combinations of benefits to distinct groups of voters, thereby biasing electoral competition, to the benefit of more intense voters and better-endowed parties.