On 14 January 2017, party leaders in federal committee formally set the congress' date for 17 and 18 June with a primary election scheduled for May, the preferred choice of both Javier Fernández and Susana Díaz who had called for postponing the congress' date to "just before summer [2017]" in hopes of Sánchez's support eroding over time.
Despite previous calls from critics for the leadership contest to be held earlier, the proposed timetable was reluctantly accepted by critics with little opposition as Fernández and Díaz's faction commanded a comfortable majority among federal committee members.
The next day, Patxi López unexpectedly became the first to publicly announce his candidacy to the party's leadership, stating that the party's abstention in Rajoy's investiture had been "an error" and claiming to "feel strong enough to rebuild the party".
After weeks of waiting for Sánchez's final decision and of debating on whether it was advisable for the late Secretary General to return to office, many of his previous supporters switched sides and aligned with López, appealed by his 'third way' project, while calling for Sánchez to join them in an effort to prevent splitting the anti-Díaz vote.
Among those withdrawing their support from the former party leader were Balearic President Francina Armengol—the only PSOE regional premier not aligned to Susana Díaz—as well as the party's regional branches in Madrid, the Basque Country, Navarre, Castile and León and La Rioja.
Even the PSC, formerly staunch defenders of Sánchez before his deposition, now claimed "neutrality" by virtue of Iceta's agreement with Díaz.

Pedro Sánchez, who was said to be privately upset by López's move—both had been close allies during his time as Secretary General—, revealed on 18 January he would be meeting party members throughout Spain without clarifying whether he would withdraw from the race or not.
Moreover, sources from within his team hinted that he had allegedly already chosen to run, but that he would not make the decision public until it better suited him, instead focusing in warming up his potential candidacy with events widely seen as a defiance to his rivals, such as one scheduled in Seville—Díaz's home province—for 28 January.
It was later revealed that López was among those who advised Sánchez to resign his seat, a move which deprived him of a public platform from where to launch his leadership run and for which Sánchez was said to feel "deeply betrayed".
Concurrently, Susana Díaz was determined to launch her bid in the ensuing weeks and started assembling campaign teams in the different PSOE regional federations to ready up the party's "machinery" under her control for collecting endorsements once the race would formally start.
López's announcement, which was said to initially catch Díaz unprepared, did not alter her plans and, like Sánchez, she remained silent on her intentions to run, aware that her bid for the highest party office would rush a succession race within her party in Andalusia.
Some suggested Díaz would try to combine her role as President of the Regional Government of Andalusia with that of PSOE Secretary General if elected.

While Patxi López had been the first to announce his run and had quickly seen the anti-Díaz coalition coalesce around him, he did not obtain the express support of historical party leaders and long-time friends such as Alfredo Pérez Rubalcaba—who disassociated himself from Lopez's strategy and praised Díaz's "political strength"—. He also stirred up suspicions among Pedro Sánchez's remaining loyalists that his move was an opportunistic maneuver aimed at thwarting Sánchez's potential bid and negotiating a future power sharing with Díaz, despite López's calls that he was willing to "go to the end" in the fight for PSOE's control.
Sánchez found himself stranded from most of his previous collaborators and could no longer count with the party apparatus of the anti-Díaz regional federations to back him, facing the challenge of making up a minimal infrastructure able to grant his campaign the required resource
On 14 January 2017, party leaders in federal committee formally set the congress' date for 17 and 18 June with a primary election scheduled for May, the preferred choice of both Javier Fernández and Susana Díaz who had called for postponing the congress' date to "just before summer [2017]" in hopes of Sánchez's support eroding over time. Despite previous calls from critics for the leadership contest to be held earlier, the proposed timetable was reluctantly accepted by critics with little opposition as Fernández and Díaz's faction commanded a comfortable majority among federal committee members. The next day, Patxi López unexpectedly became the first to publicly announce his candidacy to the party's leadership, stating that the party's abstention in Rajoy's investiture had been "an error" and claiming to "feel strong enough to rebuild the party". After weeks of waiting for Sánchez's final decision and of debating on whether it was advisable for the late Secretary General to return to office, many of his previous supporters switched sides and aligned with López, appealed by his 'third way' project, while calling for Sánchez to join them in an effort to prevent splitting the anti-Díaz vote. Among those withdrawing their support from the former party leader were Balearic President Francina Armengol—the only PSOE regional premier not aligned to Susana Díaz—as well as the party's regional branches in Madrid, the Basque Country, Navarre, Castile and León and La Rioja. Even the PSC, formerly staunch defenders of Sánchez before his deposition, now claimed "neutrality" by virtue of Iceta's agreement with Díaz.
Pedro Sánchez, who was said to be privately upset by López's move—both had been close allies during his time as Secretary General—, revealed on 18 January he would be meeting party members throughout Spain without clarifying whether he would withdraw from the race or not. Moreover, sources from within his team hinted that he had allegedly already chosen to run, but that he would not make the decision public until it better suited him, instead focusing in warming up his potential candidacy with events widely seen as a defiance to his rivals, such as one scheduled in Seville—Díaz's home province—for 28 January. It was later revealed that López was among those who advised Sánchez to resign his seat, a move which deprived him of a public platform from where to launch his leadership run and for which Sánchez was said to feel "deeply betrayed". Concurrently, Susana Díaz was determined to launch her bid in the ensuing weeks and started assembling campaign teams in the different PSOE regional federations to ready up the party's "machinery" under her control for collecting endorsements once the race would formally start. López's announcement, which was said to initially catch Díaz unprepared, did not alter her plans and, like Sánchez, she remained silent on her intentions to run, aware that her bid for the highest party office would rush a succession race within her party in Andalusia. Some suggested Díaz would try to combine her role as President of the Regional Government of Andalusia with that of PSOE Secretary General if elected.
While Patxi López had been the first to announce his run and had quickly seen the anti-Díaz coalition coalesce around him, he did not obtain the express support of historical party leaders and long-time friends such as Alfredo Pérez Rubalcaba—who disassociated himself from Lopez's strategy and praised Díaz's "political strength"—. He also stirred up suspicions among Pedro Sánchez's remaining loyalists that his move was an opportunistic maneuver aimed at thwarting Sánchez's potential bid and negotiating a future power sharing with Díaz, despite López's calls that he was willing to "go to the end" in the fight for PSOE's control. Sánchez found himself stranded from most of his previous collaborators and could no longer count with the party apparatus of the anti-Díaz regional federations to back him, facing the challenge of making up a minimal infrastructure able to grant his campaign the required resource
2017 PSOE leadership election