In contrast to recent decades of decentralized and leaderless social movements, the Assemblea Nacional Catalana (ANC) emerged in 2011 as a structured-based organization to lead Catalonia’s pro-independence movement. Building on a grassroots movement that organized unofficial municipal referendums (2009–2011), the ANC played a pivotal role in Catalonia’s push for independence.
This paper examines the ANC’s unique structure and capacity to mobilize support to influence election outcomes. To this goal, I first assess the factors behind the branches’ expansion and find that in the early phases, mobilization leveraged existing resources, including the grassroots movement behind the Consultes. The creation of new branches also concentrated in municipalities where pro-independence parties, especially small ones, had previously gained voter support. This highlights the ANC’s ability to channel existing pro-independence sentiment. While the complementary logic lost traction after 2012, the mobilization of existing resources remained important, and new branches emerged in municipalities with larger election turnouts.
Second, I estimate the ANC’s impact on pro-independence voting using Callaway and Sant’Anna’s (2021) difference-in-difference identification strategy. Municipalities that created branches early in the game saw 2–4 percentage point increases in support for pro-independence parties in key regional elections, though this effect diminished over time. The mobilization also influenced participation at the individual level, increasing attendance at key rallies in Barcelona.
This study bridges research on the dynamics of secession movements and protests, providing novel insights into how localized mobilization can shape electoral outcomes, stressing the importance of structured grassroots social movements.