The article is based on a comparative analysis of political institutions in Armenia, Belarus, Kazakhstan, Kyrgyzstan, and Russia - the members of the Eurasian Economic Union (EAEU). The author shows that political institutions in these countries have a number of distinctive characteristics and common features. The latter include a lack of developed party system; the presence of strong institutions of the presidency and of the ruling “party of power”, as well as informal political institutions and practices. Based on an analysis of in-depth interviews with the experts from Armenia, Belarus, and Kazakhstan, the author concludes that these countries tend to form ethnic rather than civil nations and identities, which results in the underdevelopment of political institutions. However, due to increasing global and domestic socio-political instability, and worldwide technological and socio-cultural shifts, political institutions in the EAEU countries are forced to adapt to new conditions and undergo transformations. The author shows that the processes of adaptation and transformation of political institutions are more intense in Armenia and in Kyrgyzstan. However, this is closely related to increases in domestic instability and change of power in these countries, while in Belarus, Kazakhstan, and Russia, these processes are more gradual and long-lasting. Still, such a duration comes along with the risk of delay in the necessary political changes. The article predicts an increase in socio-political instability and the rate of change of political institutions in the EAEU countries in the 2020s, which is associated with the consequences of global technological, sociocultural, and geopolitical shifts.