The leader of the mensheviks was
lenin
trotsky
martov
nicholas

The leader of the Mensheviks was Martov.  

The Mensheviks were the moderate fraction of the Russian Social Democratic Labor Party that emerged from its second congress in the summer of 1903 after the dispute between Vladimir Lenin and Yuli Martov. Differentiated current within Russian Marxism, it became a separate party in 1912. It had a prominent role in the inter-revolutionary period of 1917, both for its control of the Petrograd Soviet and the All Russian Central Executive Committee and for its participation in the provisional government overthrown in the October Revolution.

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