Popular fronts

Popular fronts were combinations of Communists, Socialistss, and sympathetic leftists. The idea was first tried, unsuccessfully, in France during World War II in an attempt to resist the Nazis.

Popular fronts in The Gladiator
In one alternate, the United States' weak resolve in fighting global Communism gave rise to popular fronts in Europe, which successfully swung their respective countries away from the US and towards the Soviet Union. The education system of that alternate taught that while Communism's ultimate triumph was inevitable, the popular fronts brought victory that much sooner, with a minimum of violence.