How did civil rights issues both unite and divide society in the United States during this time period?

Socialist participation in the communist-inspired Popular Front was an electoral strategy during the mid-1930s that was meant to check the rapid advance of facism and other antidemocratic movements that were gaining ground at this time. In both Spain and France, for example, socialists played a pivotal role in forging a political alliance that embraced a wide spectrum of left and liberal factions. However, in Spain the Popular Front government formed in February 1936 was short lived, as civil war broke out in July. In France, Léon Blum's (1872-1950) socialist-led Popular Front coalition also enjoyed only limited success between 1936 and 1938. In this brief period, Blum managed to push through a number of social reform measures, such as the implementation of the forty-hour work week, before his government succumbed to the pressures of its conservative and pro-appeasement rivals.

What time period in history?