The majority stayed within the mainstream party but a minority, who supported the Bolshevik path became known as Left Socialist-Revolutionaries. They in effect split from the main party and in the elections to the Constituent Assembly often stood as left-SRs against the mainstream party (although with little electoral success).

Many left-SRs joined the Soviet government after the Bolshevik takeover of October, 1917, although those that did resigned their positions in protest at the signing of the Treaty of Brest-Litovsk. The left-SRs were implicated in the assassination of the German ambassador to the Soviet Union.