In 1917, the Socialist Revolutionary Party split between those who supported the Russian Provisional Government, established after the February Revolution; and those who supported the Bolsheviks, who favoured a communist insurrection. The majority stayed within the mainstream party, but a minority who supported the Bolshevik path became known as Left Socialist-Revolutionaries or Left SRs.
Maria Spiridonova was a prominent leader of the Left SRs. They split from the main party, but the split was not completed before the Russian Constituent Assembly elections. The first meaningful electoral test between the parties in the peasant soviets a few weeks after the Assembly elections showed the parties had roughly equal support among the peasantry.
The Left SRs departed the Socialist Revolutionary Party due to their support for the overthrow of the Alexander Kerensky government. The Left SRs would later support the Bolsheviks who came to overthrow the provisional government.
The Left SRs made the following demands:
The Left SRs became the coalition partner of the Bolsheviks in the Soviet Government (the Council of People's Commissars) after the October Revolution of 1917, heading the People's Commissariats for agriculture, justice, posts and telegraph. They later resigned their positions in protest at the signing (3 March 1918) and ratification of the Treaty of Brest-Litovsk, but they continued for a time to co-operate with the Bolsheviks at other levels.