Abstract Is political polarization in Indonesia here to stay? For years, scholarly consensus on partisanship in Indonesia viewed weak partisan identity, collusive party behavior, and the predominance of personality as features of a system that would prevent the emergence of deep polarization. In the wake of religious and ethnic mobilizations during three contentious elections, the question of whether polarization has come to Indonesia is increasingly salient. Where previous studies have focused on elite polarization, we focus on whether polarization has a mass base. Using an original, nationally representative survey of 1,520 Indonesian adults shortly before the 2019 election, we tested whether political preferences in Indonesia reflected any of four underlying sets of resentment—religious, anti-Chinese, anti-Java, or regional. We found links of varying strength between each of these resentments and political preferences. Analyzing the sources of resentments, we find evidence that different resentments may travel through different channels: religious resentment through organizational membership, anti-Chinese resentment through exposure to social media, regional resentment through awareness of regional resource disparities, and resentment of Java through having experienced the old politics of Java—Outer Islands conflict. These links between political affiliation and resentment suggest that polarization is here to stay, so long as politicians make use of real, underlying resentments.