In 1938, Abern helped found the Socialist Workers Party (SWP) and he was on the National Committee of that organization from 1938 until 1940. The April 1940 convention of the SWP instructed the National Committee of the party to take disciplinary action against Abern, Shachtman, James Burnham, and their factional supporters if that group failed to abide by the decisions of the convention. In accordance with these instructions, the National Committee suspended Burnham, Shachtman, and Abern at its meeting of April 22, 1940, giving the members of this so-called "petty-bourgeois opposition" an opportunity to recant and return to the party. Burnham left the radical movement at this time, while Abern joined Max Shachtman's in establishing a new organization called the Workers Party of the United States (WPUS). The pair were expelled from the SWP by a Plenum Conference held in Chicago from Sept. 27 to 29, 1940.