Article Party (de)institutionalization in times of political uncertainty: The case of the Justice and Development Party in Turkey S ¸ ebnem Yardımcı-Geyikc ¸i Hacettepe University, Turkey Hakan Yavuzyilmaz Nottingham University, UK Abstract Recently many polities around the world as different as Hungary, Turkey, Venezuela, Thailand suffer from autocratization. This has led to a growing scholarly interest in the process of autocratization. Yet, despite this emerging generation of studies on democratic setbacks, we still do not know much about the changing nature of party politics in the process of autocratization. We argue, in this article, that during autocratization, the incumbent party follows the path of internal and external party deinstitutionalization in response to the changing nature and intensity of political uncertainties. Using the case of the Justice and Development Party in Turkey, we address three questions: (1) How can the concept of party de- institutionalization be revised and used to understand party transformation during autocratization? (2) What explains party deinstitutionalization in transitional contexts? (3) What is the relationship between party de-institutionalization and autocratization? In doing so, this article increases our understanding of party transformation in transitional contexts and more specifically incumbent party change in the process of autocratization by providing a causal theory of party deinstitutionalization. Keywords autocratization, party change, party deinstitutionalization, the Justice and Development Party, Turkey, electoral authoritarianism Introduction Recently many polities around the world as different as Hungary, Turkey, Venezuela, Thailand suffer from auto- cratization which is defined as “a process of regime change towards autocracy” (Cassani and Tomini, 2019). Coming to power through free and fair elections, populist leaders in these countries have begun to play with the democratic rules of the political game—impairing institutional checks and balances, eroding the freedom of media, violating political rights and freedoms, and intimidating the opposi- tion forces (see Levitsky and Way, 2010). As such, move from democracies toward electoral democracies, electoral authoritarian regimes in the hands of populist leaders has become a salient global challenge affecting several coun- tries (see Lu ¨hrmann and Lindberg, 2019). This has led to a growing scholarly interest in the process of autocratization (see Cassani and Tomini, 2019; Diamond, 2015; Haggard and Kaufmann, 2016; Levitsky and Ziblatt, 2018). Yet, despite this emerging generation of studies on democratic setbacks, we still do not know much about the changing nature of party politics in the process of autocratization. Put differently, the puzzle remains as to what happens to an incumbent party which emerges in a democratic context and then becomes the major agent of autocratization. We argue, in this article, that the incumbent party changes sig- nificantly during the process of autocratization in order to Paper submitted 16 March 2020; accepted for publication 31 August 2020 Corresponding author: Sebnem Yardimci-Geyikci, Department of Political Science and Public Administration, Hacettepe University, 06800 Ankara, Turkey. Email: sebnemyardimci@gmail.com Party Politics 1–14 ª The Author(s) 2020 Article reuse guidelines: sagepub.com/journals-permissions DOI: 10.1177/1354068820960010 journals.sagepub.com/home/ppq