In this article, we will probe two distinct historical questions. First, we explore why congressional representatives from the South, who had generally supported the Democratic Party on labor issues during the 1930s, joined with Republicans to oppose the party's pro-labor orientation in the 1940s. We also examine why the class-based union movement that mobilized so assertively after the passage of the Wagner Act in 1935 became so cramped and pragmatic by the early 1950s. These puzzles, we believe, are closely related. Our explanation for why labor's horizons, topography, and prospects constricted to workplace issues, to some segments of the working population, and to limited geographic areas by the end of the Truman years points to how southern Democrats shaped the main institutions produced by New Deal and Fair Deal labor legislation.