Following the negative results of the Catalunya Sí que es Pot alliance in the 2015 Catalan regional election, Podemos, Initiative for Catalonia Greens and United and Alternative Left started negotiations with Barcelona en Comú—Barcelona mayor Ada Colau's party—to form a joint list to contest the upcoming general election in Catalonia. An agreement was reached on 28 October 2015 to constitute an alliance under the "En Comú Podem" label, aiming at mirroring Colau's success in the 2015 Barcelona local election. If successful, the alliance was planned to be maintained in a permanent level ahead of future electoral contests. The candidacy was to be led into the election by historian Xavier Domènech, comprising members from Podemos, ICV, EUiA, Barcelona en Comú and Equo and featuring Colau herself in a "symbolic" position in the list for Barcelona. Under the promise of holding a legal and binding referendum on independence if accessing the national government, En Comú Podem emerged as the largest force in Catalonia in the 20 Decembergeneral election, securing 24.7% of the share and 12 seats in the Congress of Deputies. The alliance was renewed for the 2016 general election, with an unsuccessful attempt to incorporate Pirates of Catalonia into the lists despite the party having initially expressed interest in doing so. ECP maintained its status as the largest political list in Catalonia on 26 June, but fell short of achieving a landslide victory at the scale predicted by opinion polls. ECP initially aimed at forming its own parliamentary group, separately from Podemos. However, this move was blocked by the board of the Congress of Deputies as a result of ECP being a coalition comprising Podemos—which had also contested the general election elsewhere in Spain—and due to the legal impossibility for parties "not competing each other in the election" to form separate groups, forcing ECP-elected deputies to join a "confederal" group with Podemos. In the electoral repetition of 2016, and in order to try to circumvent this legal clause, the newly-established Unidos Podemos alliance signed that it would not be running in Catalonia as ECP would stand as a political party within an "instrumental" coalition, in order to preserve its previous electoral rights. This ultimately proved to not be enough, and in July 2016, ECP renounced to form its own group and joined Unidos Podemos's one, though it would attempt to reform the Congress's regulations for them to allow the formation of such group throughout the term of the resulting parliament. After the launching of Más País by former Podemos founder Íñigo Errejón ahead of the November 2019 Spanish general election and his announcement of a general agreement with Equo to run in alliance in a number of constituencies, including Barcelona, Equo's branch in Catalonia refused to join Errejón's lists and pledged its support to the En Comú Podem alliance.
