While parties in many new democracies frequently split, merge, change their labels, disappear, and form and dissolve electoral alliances, the research on these transformations is limited. This study seeks to address this gap in the literature in two ways. First, it uncovers the dimensionality of party instability in 11 countries in Central and Eastern Europe in the period between 1990 and 2012 by conducting factor and correspondence analysis at the level of parties and electoral periods. Three alternative theoretical perspectives are tested: (1) no relationship between different forms of party instability, (2) party instability is a unidimensional phenomenon, (3) two dimensions of party instability (party consolidation and party fragmentation). Second, as an important step towards understanding the causes and consequences of party instability, the study also examines the relationship between party instability and the fragmentation, programmatic structuration and polarization of party systems.
