This article explores the evolution of social movement politics under the Democratic Progressive Party (DPP) government (2000–2004) by using the perspective of political opportunity structure. Recent “contentious politics” in Taiwan is analyzed in terms of four changing dimensions of the opportunity structure. First, the DPP government opens some policy channels, and social movement activists are given chances to work within the institution. Yet other features of the political landscape are less favorable to movement activists. Incumbent elites' political orientation shifts. As the economic recession sets in, there is a conservative policy turn. Political instability incurs widespread countermoblization to limit reform. Last, the Pan-Blue camp, now in opposition, devises its own social movement strategy. Some social movement issues gain political salience as a consequence of the intervention of the opposition parties, but its excessive opportunism also encourages the revolt of antireform forces. As a result of these countervailing factors, social movements have made only limited gains from the recent turnover of power.