Why do well-designed political institutions backfire? This article examines one particular institutional constellation consisting of hierarchical and horizontal linkage institutions. It argues that weaker institutions are subject to "gravitational attraction" to stronger linkage institutions, and the latter distorts and converts the former. The institutional conversion of weaker institutions follows three steps: a priority change, an adaptive coping strategy and the accumulation of nonconventional activities. This study unpacks the inner workings of China's petition system, originally designed as a consultative political institution, and examines how it has been converted into a repressive one under the pressure of stronger coercive institutions. This research challenges the myth of authoritarian institutions in the study of comparative authoritarianism.