Parliamentary effectiveness was both crucial to the communist successor parties' access to decision-making and more difficult to achieve than any of the other dimensions of party regeneration. The task ahead was as daunting as it was significant – parliaments were central to post-1989 politics in the region, both because they were responsible for legislating the future shape of the political and economic systems and because they were the main wellspring for new political parties and their interactions. The communist successors themselves immediately recognized that parliamentary performance would serve as one of the main standards by which they would be judged by voters and competitors alike. Given their initial electoral defeats and lack of alliances, the parliament was one arena in which the successor parties could prove themselves in the first few years following the democratic transition.

Parliamentary effectiveness consisted of acceptance by other parties and cohesiveness of the party's parliamentary grouping. Parliamentary acceptance is the extent to which a given party is able to establish cooperation with other parties and is considered for potential government posts and coalitions. In the parliamentary systems considered here, such acceptance comprised the potential to participate in government and in opposition coalitions, informal party alliances, and membership in parliamentary committees. As we will see, the parties' historical record, and specifically the reputations engendered by the earlier conflict between the communist party and society, were chiefly responsible for their parliamentary acceptance – or lack thereof.