The Socialist Party of America was established on 29 July 1901 as a result of a merger between the moderate wing of the Socialist Labor Party and the Social Democratic Party. For most of its turbulent history, the Socialist Party has been reformist in its political attitudes and democratic in its organization. Until the mid 1950s, the Socialist Party advocated trade unionism, supported an evolutionary rather than a revolutionary conversion to socialism, and endorsed progressive as well as socialist candidates for public office.

Between 1901 and 1912, the party's membership grew from 10,000 to 118,000 and the votes cast for socialist Presidential candidates increased proportionately from 100,000 to 900,000. By advocating reform of the political and economic system, the party was able to enlist the support of many orthodox socialists and many heterogeneous elements remaining from such progressive movements as the Greenbackers, Populists, and "Single Taxers". The result was a broad based party, particularly strong in the West, which was prepared to sacrifice ideological purity for numbers and revolutionary gains for immediate political success. Evidence of this policy was demonstrated in the fact that in 1912 there were 56 socialist mayors, over 300 socialist aldermen, many socialist state legislators, and one socialist member of the House of Representatives.

This success, however, was short lived. Throughout the 1910s and 1920s, the Socialist Party suffered from the same external pressures which caused other progressive movements to stagnate. The party also suffered from numerous internal crises as well. Three major conflicts which caused the party to decline in this period were: (1) the expulsion of its revolutionary wing in 1912 1913; (2) the party's official opposition to World War I, which not only alienated the conservative membership of the party but also led to the trial and imprisonment of such important party figures as Eugene V. Debs and Victor Berger; and (3) the Russian Revolution of 1917, which encouraged the left wing of the party to demand a more militant program and, when this was not forthcoming, to secede from the party in 1919 and establish the Communist Party.

Following a brief resurgence in the late 1920s and early 1930s under the strong leadership of Norman Thomas, the Socialist Party was once again plagued with internal conflicts. The principal divisions within the party at this time were generational, geographical, and ideological in nature. These divisions were manifested in three major factions within the party. First, there was the "Old Guard" which was composed largely of middle aged and elderly members who had been in the party since its early years. The Old Guard occupied most of the party's leadership positions, including the office of national chairman and the National Executive Committee. Geographically, the old Guard was strongest in Pennsylvania, New York, and Connecticut, but it also controlled many of the state offices across the country.

Opposing the Old Guard were the "Militants" who were young, doctrinaire Marxists and the "Progressives" who were young, radical nonMarxists. The Militants, who resided primarily in New York City, were not communists. In fact, they were opposed to the Communist Party and they were critical of the Soviet Union's denial of civil liberties. The Progressive faction in the Socialist Party, also from New York City, was not so powerful as the Old Guard, but it was larger in size than the Militants. The Progressives, for the most part, were not Marxists. Instead, their goal was to organize a farmer labor party which would be based on principal rather than political expediency.

These three factions did not bring their differences of opinion into public focus until the 1932 Socialist Party convention in Milwaukee. During this convention, however, the groups clashed over the re election of Morris Hillquit as national chairman and two resolutions concerning the Soviet Union and trade unionism.

The conflict intensified during the New York City fur workers dispute in 1933. In the fur industry of New York City there were two rival unions, one controlled by the Old Guard and the other led by the Communist Party. During the dispute over which union should represent all of the fur workers, the Militants charged that the Old Guard was attempting to subvert the communist union in its quest for total control despite the fact that most of the workers supported the communists. Norman Thomas concurred in this view and demanded that the Old Guard cease its activities against the communist union members. The Old Guard union responded to these charges by obtaining a labor injunction against the communist union. Eventually, the fur workers dispute was resolved when members of both unions negotiated a settlement.

Another incident which pitted the three factions against each other occurred during the debate on the Declaration of Principles at the 1934 Socialist Party convention in Detroit. The Declaration of Principles was drafted by the Progressives and the Militants and included numerous statements on issues which they believed every socialist should advocate. During the debate on this document, the factions argued over the statements pertaining to socialist action in the event of war and the socialist view of democracy. When the delegates finally adopted the Declaration of Principles before the convention adjourned, it clearly demonstrated that the Old Guard was gradually losing control of the party.

The factional strife came to a climax in 1936 when the Old Guard bolted from the Socialist Party after the national convention in Cleveland and organized the Social Democratic Federation. The withdrawal of the Old Guard was a serious loss for the party. Not only did major socialist figures from New York, Connecticut, Maryland, and Pennsylvania leave the party, but they took with them much of the financial support of the party as well. In addition to these developments, two major urban political machines in the Socialist Party Reading, Pennsylvania and Bridgeport, Connecticut joined the Social Democratic Federation.

Following the departure of the old Guard, the Progressives and militants continued the party's infighting by dividing into three groups. The first group was an amalgamation of the old Progressives and the leadership of the Militants. Under the direction of Jack Altman and Paul Porter these moderates supported the American Labor Party and endorsed a more democratic view of socialism. A second group, formerly associated with the Militants, were emerging as the new left wing faction of the party. Calling itself the "Clarity" group after the periodical, Socialist Clarity, this group was led by Frank Trager, Gus Tyler, Robert and Max Delson, and Herbert Zam. Ideologically, the Clarity group was not opposed to labor parties and farm labor coalitions, but they were more insistent than the Altman group that any labor party wanting Socialist Party support should have a wide labor base and should repudiate capitalist reformist politics.

Complicating the situation within the party was an ultra left Trotskyite faction. Known as the Appeal group because of their periodical, Socialist Appeal, the Trotskyites maintained that the Socialist Party should repudiate all labor and farmer labor parties and thus transform itself into a revolutionary party. The Trotskyites also denounced the utilization of democratic means to achieve socialist objectives. From their viewpoint, a revolutionary party needed to resort to violence in order to become a significant political force in America.

These three factions clashed on a variety of issues during the late 1930s. In national convention sessions and local political campaigns, these groups differed over the Socialist Party's attitude toward preventing war, the Socialist Party's affiliation with the American League Against War and Fascism, and socialist cooperation with organized labor. By the end of 1937, the disputes between the various groups were so damaging to the conduct of party business that the National Executive Committee finally took decisive action and expelled the Trotskyite faction.

The Socialist Party never fully recovered from these setbacks, although negotiations were successful in reuniting the Social Democratic Federation with the party in 1957. Nevertheless, despite this encouraging development, the internal conflicts and the emergence of the New Left in the late 1950s and 1960s eventually caused the Socialist Party to lose its influence as an effective political organization.