Do parties represent the ideological preferences of voters in clientelistic political systems? We answer this question by studying the case of Indonesia, whose politics analysts usually describe as being based on patronage. We reassess this proposition using an original survey of over 500 Indonesian legislators. We show that, while party positions are similar on economic policy, they are differentiated on religious issues. To explore the implications of this cleavage, we develop a new measure of policy preferences about state-Islam relations, and match survey responses from legislators and citizens. Our analysis shows a high degree of congruence in party dyads of voters and politicians, which indicates that ideology is more salient than existing research suggests. We further suggest that clientelistic networks may have been pivotal in ensuring the survival of this religious-based ideological cleavage through decades of authoritarianism and democratic politics characterized by ideological moderation.