By 1940 he was part of a faction within the SWP which objected to the internal regime of that party and was developing an analyis of the USSR as a bureacratic collectivist society in which a new class, the state bureaucracy, held social and state power. In 1940 they became the Workers Party led by Max Shachtman.
By 1948 the WP believed that the prospects for revolution were receding and that it must transform itself into a propaganda group. Therefore it became the Independent Socialist League and Hal Draper continued as one of its leading writers and functionaries.
With a shrinikng membership, although its youth work was bouyant, the ISL leadership around Shachtman decided that the time had come to join forces with the Socialist Party of the USA and in 1958 fused into it. This was a development that Draper opposed although he went along with for lack of an alternative orientation.
In 1962, after an ultimatum from Joel Geier later a leader of the Independent Socialists, Draper now resident in Berkeley California, formed the Independent Socialist Club (ISC) outside the SPUSA. In 1964 Draper was heavily involved in the Free Speech Movement, an important precursor of that decades New Left, on the Berkeley campus.
In 1968 ISC became the Independent Socialists as it expanded nationally. But in 1971 he quit the IS due to his concern that IS was no longer placing the working class at the centre of its analysis. From then onwards hr produced a stream of scholerly works on Marxism and the workers movement.
His most enduring legacy is likely to be his four volume study Karl Marx's Theory of Revolution. Although it's main arguments are summarised in the pamphlet The Two Souls of Socialism.
Organizations he was a member of: