Answer:
The Communist Party.
Step-by-step explanation:
The Communist Party and its allies played an important role in the United States labor movement, particularly in the 1930s and 1940s, but never succeeded, with rare exceptions, either in bringing the labor movement around to its agenda of fighting for socialism and full workers' control over industry, or in converting their influence in any particular union into membership gains for the Party. The CP has had only negligible influence in labor since its supporters' defeat in internal union political battles in the aftermath of World War II and the CIO's expulsion of the unions in which they held the most influence in 1950. After the expulsion of the Communists, organized labor in the United States began a steady decline.