The foundations for the split of the Social Democrats into Bolshevik and Menshevik factions were laid back at the Second Congress of the Russian Social Democratic Labor Party of 1903 due to different formulations about the organization of the party: the Bolsheviks, led by Lenin, demanded from the party members "personal participation", and the Mensheviks – "personal assistance". The difference in wording indicated different approaches to party building: if Lenin's followers insisted on the formation of a rigid centralized organization, an organization of "professional revolutionaries", then the Mensheviks – on free association.