Critical of both the Soviet Union and the reformist wing of the Socialist Party of America, the SLP became increasingly isolated from the majority of the American Left.

The SLP experienced another increase in support in the late 1960s and early 1970s, but then subsequently declined at a fast rate with the party last nominating a candidate for president in 1976.

German immigrants preferred the parliamentary approach employed by Ferdinand Lassalle and the fledgling Social Democratic Party of Germany while longer-term residents of America usually supported a trade union orientation.

This found expression in the Lehr und Wehr Verein (teaching and defense society), an armed and drilled body of workmen pledged to protect the workers against the militia in a strike.

Members who were displeased with the exclusively political actionist turn of the party who wanted the group to focus more on organizing workers formed the International Labor Union.

The SLP further divided the next year when Marxist Paul Grottkau was forced by the anarchists to resign as editor of the Chicago daily, the Arbeiter Zeitung.

The party's English-language organ, Bulletin of the Social Labor Movement, appeared monthly from Detroit in the shadow of the powerful Chicago German-language radical press until it was finally discontinued altogether at the end of 1883.

The party's membership situation was so dismal that the English-speaking Corresponding Secretary of the organization, Philip Van Patten, left a suicide note in April 1883 and mysteriously disappeared.

[27] At its December 1883 Baltimore Convention, the SLP made a vain effort at reestablishing organizational unity with the IWPA, adopting a particularly radical "proclamation" in the name of the party and eliminating the position of National Secretary to allow the form of decentralization favored by the anarchists.

[30][31] The party remained almost completely separated from the English-speaking workers movement and longing for leaders who could traverse the seemingly insurmountable language barrier which limited the organization to a sort of Teutonic ghetto.

Despite its active role as cheerleader and publicist, the SLP was unable to exert any sort of real influence in the Knights of Labor until it was already in steep decline toward the start of the 1890s, when it won effective control of the New York District Assembly of the K of L in 1893.

[33] In that same year, socialist delegates to the governing General Assembly of the K of L were largely responsible for the defeat of Terence Powderly and his replacement by J. R. Sovereign as Grand Master Workman, the chief executive officer of the organization.

[33] When he recanted on this pledge, a bitter feud erupted, ending with the December 1895 General Assembly refusing to seat de facto SLP party leader Daniel De Leon as a delegate from District Assembly 49, resulting in an outright break of the two organizations and withdrawal of the greater part of the New York district from the organization, thereby hastening the Knights of Labor's demise.

[40] Thereafter, De Leon moved to Texas, where he practiced law for a time before returning to Columbia University in 1883 to take a position as a lecturer on Latin American diplomacy.

[40] De Leon participated in the first Nationalist Club in New York City, a group dedicated to advancing the socialist ideas expressed by Edward Bellamy in his extremely popular novel of the day, Looking Backward (1888).

[41] The failings of the Nationalist Club movement to develop a viable program or strategy for winning political power left De Leon searching for an alternative.

De Leon never assumed the formal role of head of the organization, National Secretary, but was always recognized—by supporters and detractors alike—as the leader of the SLP through his tight editorial control of the official party press.

[50] The party's ticket, featuring Boston camera manufacturer Simon Wing and New York electrician Charles H. Matchett, appeared on the ballot in just six states and drew a total of 21,512 votes.

The employing class controlled press and school and pulpit, the Marxists believed, their ideas of the "natural" order of things stuffed the heads of their willing political servitors.

Only through collective action, trade union activities, could the working class begin to achieve consciousness of itself, the nature of the world and its purported historic mission.

However, what sort of trade unions would instill in the working class the ideas and drive to action that would lead to a revolutionary restructuring of the economic order?

On the one hand there were those who advocated the policy of "boring from within" the already-existing unions, attempting to win their memberships over to the idea of socialist reorganization of society through the force of propaganda and practical example.

Others rejected the existing network of craft unions as hopelessly reactionary bureaucracies, sometimes outright criminal in their administration, but never able to see beyond their own narrow and isolated concerns of wages, hours, recognition, and jurisdiction.

A completely new, explicitly socialist industrial union structure was required, these individuals believed, an organization established on a broad basis uniting workers of different crafts in common cause.

De Leon's opponents (primarily German-Americans, Jewish immigrants of various origins and trade unionists led by Henry Slobodin and Morris Hillquit) left the SLP in 1899.

In July 1908, the SLP briefly made national news with the nomination of Martin R. Preston, a convicted killer serving a 25-year prison sentence in Nevada, for President of the United States.

[53] Making the nomination on the convention floor was party leader Daniel De Leon himself, who noted that Preston had "acted as the protector of defenseless girls" during a strike and had killed a restaurateur who had threatened him with death.

[53] Despite the fact that the 32-year-old Preston was under the constitutionally mandated presidential age of 35, he was nonetheless unanimously nominated by the New York convention, which immediately notified him of their selection by telegram.

As of January 2007, the party had 77 members-at-large as well as seven sections of which four (San Francisco Bay Area, Wayne County, Cleveland and Portland) held meetings, with an average attendance of 3–6 members.

They soon had a falling out with the element that they termed "the bummery" and left to form their own rival union, also called the Industrial Workers of the World, based in Detroit.