The concept of party system institutionalization is usually applied as an explanatory framework for the process during which inter-party competition exhibits the recognisable pattern of stabilization over time. Party system institutionalization is measured with indicators based on the patterns of stability in government formation and alternation. The article presents an empirical test of the argument that a high degree of party system nationalization plays a significant role in the process of party system stabilization and routinization. In the cross-temporal comparison, the presented study explains to what extent the Czech party system’s development exhibits patterns of institutionalization. The Czech case has been selected because recent party system changes are interpreted as unprecedented
with regard to the electoral success of new political parties in 2010 and 2013. To better understand the complex party competition development over past 25 years, indicators of inflation and dispersion on the party system level are compared with the Gini- based party nationalization score.