This chapter leverages micro-level data to ascertain if, and to what extent, political Islam indeed functions as an ideological cleavage that structures political competition in Indonesia. More specifically, it analyzes a survey of about 500 Indonesian legislators. While scholars of Indonesian politics acknowledge that ideological competition in this country is grounded in the political Islam cleavage, the degree to which politicians and political parties are differentiated on the issue of state-Islam relations is an open question. This study is the first attempt to systematically measure party positions on political Islam with a survey of political elites, and it shows that, while party positions are barely distinguishable on fiscal and economic policy, Indonesian parties are indeed clearly differentiated in their views of the role of Islam in public affairs. This evidence corroborates the foundations of the book’s argument, as it shows that party ideological differentiation on political Islam is sufficient to allow for meaningful representation.