The idea that populations participate politically outside of the formal mechanisms of a political system and through mass mobilizations is a reasonably accepted part of political science orthodoxy. Since the turn of the last century, in Indonesia, as in other developing countries, populations have mobilized en masse at particular stages of their histories into nation-state building processes, as well as have been mobilized by political authorities seeking to bolster or install their regimes. In the 1960s, Sukarno increasingly sought to mobilize a range of classes and interests behind his presidency and, in 1965-66, Suharto and his military backers organized anti-communist groups behind a systematic campaign to eradicate the Communist Party and remove Sukarno. Throughout the so-called 'New Order' period (1966-98), Suharto periodically mobilized groups behind his presidency and against opponents who, in turn, engaged in occasional street demonstrations against the regime. In the mid-to-late 1990s, the opposition leader, Megawati Sukarnoputri became an important rallying point for popular dissent against Suharto and, in 1998, the student movement played a crucial role in street demonstrations which helped bring down the president after three decades of strongman rule. In the post-Suharto period, which has seen the installation of three presidents between 1998 and 2001, mass mobilizations have continued to be a striking feature of the political landscape. President Habibie mobilized progovernment militias against opponents and student demonstrators, who threatened to bring down his regime. The Muslim supporters of Abdurrahman Wahid entered the streets in their thousands to protest the parliamentary impeachment of the president. Radical Muslim groups demonstrated against US military strikes on Afghanistan and against President Megawati Sukarnoputri's initial soft stance on the strikes. Potentially, these kinds of demonstrations could undermine Megawati's presidency. However, parliamentary processes rather than street mobilizations brought the presidencies of Habibie and Abdurrahman to an end while Megawati is still seeing out her term. This article examines the political mobilizations of the late-Suharto and post-Suharto periods and asks whether these mobilizations pose a threat to Indonesia's fragile transition to democracy and to a more stable institutional political process.