Almost three decades of post-Soviet party research still leave important gaps in our understanding of the intra-regional variation in political development. This is mostly due to its focus only on a few cases and priority given to studies concern with the role of informality in structuring the political outcomes. To contribute to filling these lacunas, this study pursues two distinctive, yet intertwined research objectives: firstly, it investigates the patterns of party development and potential stabilisation in two, significantly underexplored post-Soviet republics, namely Georgia and Moldova. Secondly, it attempts to assess the role of formal institutional variables – the regime type, the electoral system, and the party funding regulations – in this process. The thesis is composed of seven chapters, each based on its own analytical framework and focus.  The key finding of my research project is that party and party systems’ development in Georgia and Moldova followed different trajectories and produced different outcomes, thus confirming that the Eurasian polities should not be treated as a uniform universe of cases. The study demonstrates that the Moldovan parties developed greater organizational stability, deeper linkage with society, and higher electoral continuity than the Georgian ones, even though parties remained quite weekly institutionalized in both countries (Chapters 2 and 3). It also challenges the conventional argument about the similarity of the Eurasian party systems by showing that Georgia embarked on a steady path towards power concentration, while in Moldova it remained more dispersed, despite a period under one-party domination (Chapter 4). The thesis confirms the role of institutional factors in shaping these diverging political outcomes, although their effects neither aligned entirely with the theoretical predictions nor were always unidirectional. Furthermore, even though originated from political elite, their consequences not necessarily met the expectations of their crafters. Along this line, the study finds that the president-oriented systems of government in Georgia were less conducive to the development of institutionalized parties and contributed to higher party system concentration than the parliament-oriented regimes in Moldova (Chapter 5). It also reveals that electoral law yielded mixed political consequences depending on the country-specific correctives (Chapter 6) – the mixed electoral design in Georgia enhanced one-party domination, but also allowed smaller formations to gain representation in single-member districts; by contrast the PR in Moldova contributed to party system fragmentation (limited to a few stabilising parties) but also helped establishing one-party dominance between 2001 and 2009. Equally importantly, the thesis emphasizes that the mainstream parties in both countries have systematically manipulated party funding regulations and employed them as tools against their political opponents, which significantly affected the political competition (Chapter 7). These findings warn against disregarding the structuring role of the formal-legal order in favour of informality. My study also demonstrates that the politico-institutional order emerged from a combination of historical legacies and contingent factors in early phases of transition (Chapter 1) were of crucial importance in determining the future political developments in both countries. Finally, by highlighting specific limits of traditional analytical tools, my findings suggest the need for a further methodological and analytical refinement of the conventional toolkit employed in post-Soviet party research.