This study explains why the British Labour Party's "left" supported the unsuccessful campaign for the formation of a "Popular Front" of the Labour, Liberal, and Communist parties in the late 1930s. The support of the Labour "left" for the campaign has often been seen as a result of Communist manipulation but here Dr. Blaazer explains it by reassessing a sixty-year period in the progressive tradition in British politics. He argues that the "left" emerged from that tradition, and that its support for a Popular Front was entirely consistent with the practice and ideas of British progressives.