Abstract: This article examines the interaction between the representatives of Bolsheviks and Left Social Revolutionaries in the regional government branches during the first half of 1918. The subject of this research is the ideological conflicts that emerged between the members of the Communist Party of the Soviet Union and the Left Social Revolutionaries in their joint activity. Considerable attention is given to classification of the ideological conflicts, as well as to identification of their causes and consequences for interaction of the representatives of both parties on the local level. These conflicts were an integral part of the Soviet bipartite system. Their manifestation began since dissolution of the government coalition of Bolsheviks and Left Social Revolutionaries. Based on the analysis of archival documents and published sources, the author describes the interaction between Bolsheviks and Left Social Revolutionaries in the local soviets. The novelty consists in classification of the conflicts between Bolsheviks and Left Social Revolutionaries, as well as in introduction into the scientific discourse of certain archival documents. The conclusion is made that despite the joint activity of the two parties aimed at strengthening of the Soviet regime, the ideological conflicts demonstrated a different perspective of Bolsheviks and Left Social Revolutionaries upon the political course of the country, as well as the methods of local governance. The escalating antagonism between the two Soviet parties eventually led to instability in the bipartite system and its collapse.