Infighting more characteristic of the Republic than of Franco regime was not by itself dangerous to the Republic. Only during the short moments it could pose a threat to the front line, and Franco didn't take advantage of the opportunity. The internal political conflicts had a negative impact on the destiny of the Republic not so much through their course, as through their outcome in May 1937.
In the first half of 1937 the underlying contradictions built up in republican camp. The communists were opposing the revolution which had burst in Spain, they believed that the revolution broke away from the Soviet pattern they tried to achieve and also prevented a victory of the Republic. With regard to the latter assumption they saw eye to eye with Azaña, Prieto and Negrin. The political center of Republic veered to the right, the communists became the center of consolidation of the Party of Order which opposed the social revolution. Largo Caballero was on side of the revolution which took place in Spain because he considered it a tool of mass mobilization required for a victory over fascism and because the revolution assigned a clear meaning to the struggle — a victory of a new society over an old one and not just preservation of Spain which had existed up to 1936. Largo Caballero and its supporters sought a model of the new society which would develop during the revolution and would match the principles of democratic socialism. After they got acquainted with the ideas defended by the syndicalists in the government, the caballerists began to incline to an idea to create a society which basic structure would comprise workers’ trade-unions.
On May 3, 1937 PSUC and Catalan nationalists provoked the armed conflicts with anarcho-syndicalists in Barcelona which were announced «an anarcho-trotskyst rebellion». In spite of the fact that the parties managed to reach the cease-fire agreement, the conflicts of May 3–6 were used by the opponents of CNT and POUM to establish control over Barcelona and begin reprisals against opposition. But for as long as Largo Caballero government had the power, the investigation of events in Barcelona could result in the discredit of PSUC and communists as a whole. Therefore, the prompt overthrow of Largo Caballero, who disagreed with the interpretation of conflicts as the anarcho-trotskyst rebellion, became a matter of principle for the communists. Thus, the overthrow of Largo planned by the communists as early as in March became an immediate task in May. On top of that, the CPS was ready to keep Largo as a formal head of the government provided that a real power and, first of all, the control over force structures would be concentrated in the hands of the block communists and PSOE «centrists».