During the period of consolidation of the Slovenian party system (1992-2010) only a few new parties (DeSUS, SMS, NSi, Zares) succeeded in entering parliament. However, only one (DeSUS) has endured over the long-term. This paper will focus on the factors determining the difference between the short-term and long-term success of new parties entering the parliamentary system. Two research approaches will be combined – a deductive and an inductive approach. The deductive approach will take account of the institutional variables (such as the characteristics of Slovenia’s electoral rules), the changing characteristics of the Slovenian party system (based on Sartori''s typology), and the characteristics of party organisation development (based on Panebianco''s organisational theory).The inductive approach will be used to gather data on the party leaders’ perceptions of the factors contributing to the success or failure of their party. A summary of the findings within the framework of the two key research approaches will be presented in relation to the successes of four comparative case studies (DeSUS, SMS, NSi, Zares).
