This paper examines how unexpected electoral outcomes reshape local social dynamics and norms. I analyze the 2009 Basque regional elections, where the banning of a political party led to over 100,000 null votes, disproportionately affecting the nationalist bloc. As a result, Basque nationalists lost control of the regional government to Basque non-nationalists for the first time. This unprecedented outcome triggered an identity backlash, altering social behaviors within and across identity groups.

To study this phenomenon, I use a novel onomastic dataset of newborns’ names to capture identity-driven household decisions: the Basque Name Index (BNI). Distinctively Basque (Spanish) names are interpreted as an increased effort by parents to signal their identity to the community in opposition to the other group. Moreover, I use vote shares as proxy of communities´ identity preferences.

By combining municipal-level electoral data with BNI trends and controlling for parental characteristics, I find that in electorally competitive municipalities, where both identities coexist, backlash emerged captured by a greater dispersion in the BNI. In contrast, strongholds (whether nationalist or non-nationalist) saw reinforcement of the dominant identity.

This study highlights how electoral outcomes impacts social behavior by revealing the previously hidden political preferences of the community which affect pre-established norms. Polarization and identity-based responses might result in cases where the election outcome is unexpected.