Party Bans: Deterrence or Backlash? Evidence from the Basque Country

This paper investigates the electoral effects of party bans, studying the case of the ban on Batasuna, the political wing of ETA. In an initial electoral term, in 2003, Batasuna was banned from contesting local elections in all Basque municipalities; in a second term, in 2007, it was banned only in a subset of them, and in 2011 it became legal again. Exploiting the finite and heterogeneous length of the ban across municipalities, I find that a longer ban has a negative effect on electoral support for the targeted party. This effect is explained by the extent of the immediate loss in support in treated municipalities under the 2007 ban, observable in this instance because Batasuna called for a null vote. This pattern and further heterogeneous effects are consistent with voters learning from the new electoral scenario rather than with a direct cost attributable to the party no longer having institutional representation. This suggests that party bans may be used by incumbents to reduce their challengers' strength by triggering an electoral reshuffling, with voters learning about new parties and potentially switching allegiances.