It will be most instructive to discuss Students for a Democratic Society under two headings: "Early SDS" and "Late SDS."
The organization originally descended from a group called the Student League for Industrial Democracy (SLID), which was formed in 1930 by members of the League for Industrial Democracy (LID), itself founded in 1905 as the Intercollegiate Socialist Society by Jack London, Upton Sinclair, and other radicals of the time. LID had always worked closely with (and had overlapping membership in) the Socialist party. According to Joseph Conlin:
LID's history paralleled that of the larger party. With the waxing of American Communism during the late 1920s and 1930s, the Socialist Party, and LID with it, drifted into an anti-revolutionary reformist politics, filling a niche between the mainstream liberals and the revolutionist, pro-Soviet Communists. Like Norman Thomas, its leader for almost forty years, the party functioned somewhat as the conscience of the liberals. Socialist policies did not really differ from what the New Dealers preached. Simply, the Socialists believed in ideas the New Dealers found merely useful. 1
SLID was perhaps the main student group on the anticommunist left during the 1930s and represented the Socialist opposition to the National Student Union, a Communist-controlled organization active on many campuses. These two groups later "merged to form the American Student Union, which died a few years later, torn apart by an internal struggle between Socialists and Communists." 2
After World War II, SLID was temporarily revived, but it soon faltered again, due in part to the political climate of the McCarthy era. In 1960 it was revived again by young activists who oriented it toward direct-action tactics. This was accomplished principally by students from the University of Michigan, who officially formed SDS in the summer of 1962 at Port Huron. Predominant among these students was Al Haber. Although Haber quickly fell out with the increasing radicalization of SDS, it was his vision of direct action as an organizing tool that shaped the course of the organization.