Arguably the greatest journalist of his era and longtime editor of the famed newsletter, I. F. Stone has employed both pen and voice to support many of the nation's great left-oriented movements during the post-World War I era. Indeed, in certain ways, his career serves as a lens through which to view the American left during that span. At various times, while working for a series of leading liberal and left-wing newspapers and journals, Stone applauded La Follette's Progressive Party, Thomas' Socialist Party, the New Deal, the Popular Front, Henry Wallace's presidential bid, the anti-nuclear effort, the civil rights movement, and the campaign against the Vietnam War.

Stone's ideological development more specifically parallels the passage undertaken by Western democratic socialists. After an atypical youthful flirtation with anarcho-communism, he found attractive the brand of democratic socialism offered by Thomas and the American socialists. Economic collapse and fascist aggression, however, caused Stone and many non-sectarian radicals to back attempts by social democrats overseas and by New Dealers at home to reform capitalist economies, while continuing to urge greater structural transformation. The need for wartime mobilization resulted in exhortations by Stone and other democratic socialists for more comprehensive planning. When World War II ended, they considered extensive planning essential to produce full employment and consistent growth, and to lead their states toward the good society. During the postwar period, the earlier socialist emphasis upon the need for nationalization and the abolition of private property lessened. Some began to consider the formation of welfare states sufficient; others such as Stone relinquished their once firm convictions, because of developments within Eastern Europe, that "socialization" of property would necessarily result in human betterment. But unlike many former progressives, Stone continued to doggedly argue that a "synthesis of socialism and freedom" remained the most urgent task of the modern era. His non-doctrinaire, yet consistently radical approach, enabled the journalist to attain a position as a fixture on the American democratic left, one paralleled by only a few, including Muste, Baldwin, and Thomas.