2016 PSOE leadership crisis

A leadership crisis emerged within the Spanish Socialist Workers' Party (PSOE), starting on 26 September 2016, amid internal party dissatisfaction with the party's secretary-general, Pedro Sánchez, and a string of election losses and poor results. These circumstances resulted in a party revolt to force Sánchez's dismissal on 28 September, in an episode lasting until 1 October. The ensuing power vacuum and Sánchez's replacement by an interim managing committee, coupled with the party's U-turn to allow a minority government under the People's Party (PP) and its leader, Mariano Rajoy, after a 10-month deadlock on government formation, and the resulting worsening of relations with its sister party in Catalonia, the Socialists' Party of Catalonia (PSC), triggered a crisis of a scale unprecedented in the party's 137 years of existence.

The then president of Andalusia, Susana Díaz, had been long considered the most prominent critic of Sánchez and a potential contender for the party's leadership, being the leader of the largest and most important PSOE regional branch and, for years, the only person within the party holding an institutional position of relevance. Ever since Sánchez's first election as PSOE leader—helped by Díaz's own manoeuvres to hold off Eduardo Madina—distrust and rivalry over the party's leadership and political strategy increased between the two.

After the 2015 and 2016 general elections had resulted in the worst electoral results for the PSOE in its recent history, pressure on Sánchez increased. His record as party leader had alienated many of his former allies and pushed them towards Díaz's sphere. The immediate trigger to the crisis was the poor PSOE showing in the Basque and Galician elections in September 2016, which led critics to call for Sánchez's resignation. Sánchez held out and responded by announcing a party leadership race for October–December which he would contest, enraging dissenters and prompting half the members of the party executive committee—the party's day-to-day ruling body—to resign on 28 September. Sánchez refused to step down and entrenched himself within the party's headquarters, generating the largest crisis in the PSOE's history as neither side acknowledged the legitimacy of the other to act in the party's behalf. This situation ended when Sánchez resigned after losing a key ballot in a meeting of the party's federal committee on 1 October, being replaced by a caretaker committee and leaving behind a shattered PSOE.

Commentators predicted that this set of events would allow the party to abstain in a hypothetical Rajoy's investiture, something which was confirmed on 23 October when the party's federal committee chose to backflip and allow the formation of a new PP government in order to prevent a third election from happening. The PSC—associated with the PSOE since 1978—would not abide by the committee's decision and break party discipline, together with eight other PSOE deputies which rejected allowing Rajoy's investiture as prime minister of Spain. Sánchez resigned his seat in the Congress of Deputies and announced a new run for the PSOE leadership in the incoming leadership contest in May 2017, which he would win handily.