Instead, they opted for the Guanyem Barcelona formula, popular unity municipal candidacies comprising different parties and social movements.

[2] United Left (IU), the traditional left-wing third party of Spain, also started debating whether to join these local coalitions.

[5] Another national party that decided to participate in most of these unitary candidacies was Equo,[6] as well as minoritary parties like For a Fairer World (PUM+J), Building the Left–Socialist Alternative (CLI–AS), Republican Alternative (ALTER), Renewal–Nationalist Brotherhood (Anova), or Initiative for Catalonia Greens (ICV).

[7][8][9] The unitary lists also included individuals from social movements like the anti-eviction PAH, 15M, o the so-called mareas (Spanish for "tides") made up of workers from different service sectors like teachers, Public Health System workers or young people forced to migrate as a consequence of the 2008–15 Spanish financial crisis.

[11] Voting for the local assemblies was on the basis of universal suffrage, which comprised all nationals over 18 years of age, registered and residing in the corresponding municipality and in full enjoyment of their political rights, as well as resident non-national European citizens and those whose country of origin allowed Spanish nationals to vote in their own elections by virtue of a treaty.

This did not apply to municipalities which, as a result of their geographical location or the convenience of a better management of municipal interests or other circumstances, made it advisable to be organized through the open council system (Spanish: régimen de concejo abierto), in which voters would directly elect the local major.