Abstract-The successful Defending Islam campaign against former Jakarta governor Basuki TjahajaPurnama is clear evidence that Islamism is rising in post-Reformasi Indonesia, something that is not wellanalyzed in recent scholarships on Indonesian Islam. Influenced strongly by Civil Islam thesis, they have failed to study hardline Islamic movements due to its premises that: 1) the dominant mode of Islamic discourse in Indonesia is the moderate Islam represented by organizations such as Nahdlatul Ulama (NU) and Muhammadiyah, and 2) hardline Islamism represents a fringe element to the moderate theological discourses embedded in Indonesian Islam.I argue that rising Islamism in Indonesia is attributed to the following factors: Hardline Islamist groups are able to promote their exclusivist public theologies using the following mechanisms: 1) Appealing for solidarity and common experiences as Indonesian Muslims to persuade more moderate Muslims to join their activities, 2) Using religious propagation (da'wa) institutions such as campus da'wa groups, state companies and bureaucratic institutions, and social media outlets to promote their theological viewpoints to Indonesian Muslims, and 3) Seeking out allies in national and local government in order to have their policy agenda (e.g., restrictions against religious minorities) implemented at both national and local levels. Meanwhile, moderate civil Islamic groups are losing their appeal because these groups (particularly NU and Muhammadiyah) have moved their central focus from religious propagation to social activism and politics.