In the aftermath of 2014 European Parliament election in Spain, PSOE's national leader Alfredo Pérez Rubalcaba resigned and a leadership contest was held.

Díaz, who still had not won any major election, did not run,[11] but a coalition of regional leaders including herself, opposed the candidacy of early front-runner Eduardo Madina, who was seen as Rubalcaba's heir, and supported a change in the party's policies.

During the 2015 Andalusian parliamentary election, Díaz led a forceful campaign against Prime Minister Mariano Rajoy, opposing the austerity policies enacted by his central government.

After a long period of three-way negotiations with the two new parties, Diaz agreed with Citizens, and in early May 2015, she was subsequently re-elected as regional President.

Prime Minister Mariano Rajoy's [People's Party (Spain|PP) won the most seats, but refused to form a government as a majority of the Congress of Deputies were hostile to him.

[17] However, this arrangement would not achieve parliamentary majority, and repeat general elections were held six months later in 2016 while Rajoy remained prime minister in a caretaker capacity.

[19] Despite another second-place showing as PSOE leader, Sánchez was confident he could form a government with the 180 (out of 350) deputies who opposed Rajoy and the PP, including Podemos as well as Catalan and Basque regionalist and separatist parties.

[32][33] In May 2018, national PSOE leader Pedro Sánchez filed a vote of no confidence in the government of Mariano Rajoy that placed him as Prime Minister of Spain with the support of Podemos and Catalan and Basque nationalist parties.

Citizens, Diaz's partner in Andalusia and being a party that strongly opposes these movements, withdrew their support to PSOE and Díaz, triggering a snap election.