Changing political boundaries: evidence from a party ban

Abstract

In this study we analyze whether party bans ignite ideological polarization by exacerbating pre-existing differences. We use the 2003 ban on Batasuna, a leftist Basque political platform, as case study. In the 2005 Basque regional elections EHAK-PCTV contested in its name, which enabled the outlawed party to avoid the ban. We aim to analyze these effects in the short-term, one election period later. Using a continuous treatment in a Difference-in-Difference strategy, we are able to show that municipalities react differently given their differences in baseline support to Batasuna (measured by pre-ban vote shares in regional elections), rather than by differences in the loss of institutional representation (proxied by the pre-ban share of Batasuna councilors). The latter case holds in extreme circumstances, those in which the city mayor was from Batasuna, as the material loss of the ban is more salient. We find that the banned party increased its vote share in those places where its baseline support was higher. Moreover, the nationalist bloc increased its size while the federal bloc lost support, redefining group boundaries. We argue that the ban reinforced the ethnic identity political cleavage accentuating the inter-group political conflict.