Party institutionalization (PI) and party system institutionalization (PSI) are critical for processes of democratization and democratic consolidation, yet their impact and relationship have not been explored under conditions of autocratization. How does autocratization relate to party and party system stability, and how does that link manifest itself? To answer those questions, we draw evidence from Turkey to demonstrate that when autocratization occurs, stabilization at the systemic level can go hand in hand with declining levels of PI. We also conceptualize the process of stabilization at the systemic level alongside unit-level de-institutionalization as a form of systemic ossification. Ossified party systems appear stable but are continuously subject to the possibility of de-stabilization, or even implosion, due to the under-institutionalization of incumbent parties. Driving factors of such (de)stabilization are: (1) the increasing unevenness of party competition and (2) increasing levels of societal and political polarization resulting from autocratization.