In the first half of 1919, the Socialist Party had over 100,000 dues paying members; by the second half of 1921, it had been shattered. Fewer than 14,000 members remained in party ranks, with the departure of the large and well-funded Finnish Socialist Federation adding to the malaise. In September 1921, the NEC of the party determined that the time had come to end the party's historic aversion to "fusion" with other political organizations and issue an appeal declaring that the "forces of every progressive, liberal, and radical organization of the workers must be mobilized" to repel conservative assaults and "advance the industrial and political power of the working class."
This desire for common action seems to have been shared by various unions, as late in 1921 a call was issued in the name of the country's 16 major railway labor unions seeking a "Conference for Progressive Political Action" (CPPA). The CPPA was originally intended to be an umbrella organization bringing together various elements of the farmer and labor movement around a common program. Invitations to the group's founding conference were issued to members of a wide variety of "progressive" organizations of widely varied perspectives. As a result, from its inception the heterogeneous body was unable to agree on even a program or even a declaration of principles, let alone congeal into a new political party.
The Socialist Party was an enthusiastic supporter of the CPPA, and the group dominated its thinking from the start of 1922 through the first quarter of 1925. The party sought, in this period of organizational weakness, to forge lasting ties with the existing trade union movement leading in short order to a mass labor party in the United States on the British model.
A first National Conference of the CPPA was held in Chicago in February 1922, attended by 124 delegates representing a broad spectrum of labor, farmer, and political organizations. The gathering passed an "Address to the American People," stating its criticism of existing conditions and formally proposing an amorphous plan of action validating the status quo ante: the labor unions on the group's right wing to endorse labor-friendly candidates of the Democratic Party, the Socialists and Farmer-Labor Party adherents on the group's left wing to conduct their own independent campaigns. Perhaps the most important thing the CPPA did at its first National Conference, from the Socialist Party's perspective, was agree to meet again. The SP leadership understood the process of building an independent third party which could count on the allegiance of the country's trade union leadership would be a protracted process, and the mere fact of "agreement to disagree" but nevertheless meeting again was regarded as a step forward.
The communist movement also sought to pursue the strategy of bursting from its isolation through the formation of a mass Farmer-Labor Party. Finally emerged from its underground existence in 1922, the Communists' through their "legal political party," the Workers Party of America decided to send four delegates to the December 1922 gathering of the CPPA. However, the Credentials Committee, after protracted debate, strongly objected to the participation of Communist representatives in its proceedings and issued a recommendation that the representatives of the Workers Party and its youth organization not be seated. The Socialist Party's delegates were strongly in favor of the exclusion of the Communists and acted accordingly, even though the two organizations shared a vision of a party akin to the British Labour Party in which constituent political groups jointly participated while retaining their independent existence. The fissure between the organizations was thus widened.
As with the first conference, the 2nd Conference of the CPPA split over the all-important issue of an independent political party, with a proposal by five delegates of the Farmer-Labor Party calling for "independent political action by the agricultural and industrial workers through a party of their own" defeated by a vote of 52 to 64. A majority report declaring against an independent political party was instead adopted. This defeat of the bid for an independent political party cost the CPPA one its major component organizations, with the Farmer-Labor Party delegation announcing that their group would no longer affiliate with the CPPA after the close of the convention. Although the Socialists did not realize it at the time, the chances that the organization would ever be transformed into an authentic mass Farmer-Labor party of the British Labour type were greatly lessened with the departure of the FLP.
Still, the Socialists remained optimistic. The May 1923 National Convention of the SP voted, after lengthy debate, to retain its affiliation with the CPPA and to continue its work for an independent political party from within that group. The May 20 vote in favor of maintaining affiliation with the CPPA was 38-12. Failing a mass farmer-labor party from the CPPA, the Socialists sought at least a powerful presidential nominee to run in opposition to the old parties. A 3rd National Conference of the CPPA was held in St. Louis, Missouri on February 11 and 12, 1924, a gathering which punted on the issue of committing itself to the 1924 presidential campaign, deciding instead to "immediately issue a call for a convention of workers, farmers, and progressives for the purpose of taking action on nomination of candidates for the offices of President and Vice President of the United States, and on other questions that may come before the convention."
The decisive moment finally came on the 4th of July, 1924, a date which was not accidentally selected. The 1st National Convention of the CPPA was assembled in Cleveland at the city auditorium, which was packed with close to 600 delegates representing international unions, state federations of labor, branches of cooperative societies, state branches and national officers of the Socialist, Farmer-Labor, and Progressive Parties as well as the Committee of 48, state and national affiliates of the Women's Committee on Political Action, and sundry individuals. Very few farmers were in attendance.
The National Committee had previously requested that Wisconsin Senator Robert M. La Follette, Sr. make a run for the presidency. The Cleveland Convention was addressed by the Senator's son, Robert M. LaFollette, Jr., who read a message from his father accepting the call and declaring that the time had come "for a militant political movement independent of the two old party organizations." LaFollette declined to lead a third party, however, seeking to protect those progressives elected nominally as Republicans and Democrats. LaFollette declared that the primary issue of the 1924 campaign was the breaking of the "combined power of the private monopoly system over the political and economic life of the American people." After the November election a new party might well be established, LaFollette stated, around which all progressives could unite.
The Socialist Party enthusiastically supported the independent candidacy of LaFollette, declining to run their own candidate in November 1924. Although the LaFollette candidacy garnered five million votes, it failed to seriously challenge the hegemony of the old parties and was regarded by the unions as a disappointing failure.
Following the election, the governing National Committee of the CPPA met in Washington, DC. While the body had a mandate from the July convention to issue a call for a convention to organize a new political party, the representatives of the critical railway unions, with the exception of William H. Johnston of the Machinists, were united in opposition to idea. The railroad unions instead proposed a motion not to hold the 1925 organizational convention. This proposal was defeated by a vote of 30 to 13. Following their defeat on this question, the railroaders on National Committee members withdrew from the meeting, announcing that they would await further instructions from their respective organizations with regards to future participation. The loss of the very unions who had brought about the CPPA spelled its demise.
A convention to decide on the formation of a new political party was nonetheless scheduled by the National Committee for February 21, 1925, to be held in Chicago. Labor, the official organ of the railway unions, did nothing to promote this 2nd Convention of the CPPA, stating that since the executives of the various unions had taken no stance on the matter, it would be up to subordinate sections to consider sending delegates themselves.
The February 1925 convention found its task was virtually insurmountable, however, as the heterogeneous organization had split over the fundamental question of realignment of the major parties via the primary elections process as opposed to establishment of a new competitive political party. The railway unions, whose efforts who had originally brought the CPPA into existence, were fairly solidly united against the Third Party tactic, instead favoring continuation of the CPPA as a sort of pressure group for progressive change within the structure of the Democratic and Republican parties.
L. E. Sheppard, President of the Order of Railway Conductors of America, presented a resolution calling for a continuation of the CPPA on non-partisan lines as a political pressure group. This proposal was met by an amendment by Morris Hillquit of the Socialist Party, who called the five million votes cast for LaFollette an ecouraging beginning and urged action for establishment of an American Labor Party on the British model — in which constituent groups retained their organizational autonomy within the larger umbrella organization. A third proposal was made by J.A.H. Hopkins of the Committee of Forty-Eight, which called for establishment of a Progressive Party built around individual enrollments. No vote was ever taken by the convention on any of the three proposals mooted. Instead, after some debate the convention was unanimously adjourned sine die — bringing an abrupt end to the Conference for Progressive Political Action.
Eugene V. Debs addressed a "mass meeting" including delegates of the convention in a keynote address delivered at the Lexington Hotel early in the afternoon of February 21. After the Debs speech, those delegates favoring establishment of a new political party were then reconvened, with the opponents of an independent political party departing. The reconvened Founding Convention found itself split between adherents of a non-class Progressive Party based upon individual memberships as opposed to the Socialists' conception of a class-conscious Labor Party employing "direct affiliation" of "organizations of workers and farmers and of progressive political and educational groups who fully accept its program and principles." Following extensive debate, the Socialist counter-proposal was defeated by a vote of 93 to 64. The trade unions it coveted gone, the farmers non-existent, the Socialist Party exited the convention and abandoned the strategy of establishing a new mass party through the CPPA. A "Progressive Party" was formed by the remaining liberals, and the group survived for a short time in a limited number of states throughout the 1920s.