We study the relationship between voters' preferences and the emergence of party platforms in two-party democratic elections with adaptive parties. In the model, preferences of voters and the opposition party's platform determine an electoral landscape on which the challenging party must adaptively search for votes. We show that changes in the underlying distribution of voters' preferences result in different electoral landscapes which can be characterized by a measure of ruggedness. We find that locally adapting parties converge to moderate platforms regardless of the landscape's ruggedness. Greater ruggedness, however, tempers a party's ability to find such platforms. Thus, we are able to establish a link between the distribution of voters' preferences and the responsiveness of adaptive parties.