Shocks to issue salience and electoral competition

We propose a two party electoral competition model to analyze the effects of an exogenous shock over the relative issue salience on the strategic policy choices of the parties. We find that both parties strategically shift their policy choices from their ideal points towards the ideal point of the median voter of the newly salient issue. The polarization of the distribution of the voters preferences produces a disadvantage for one of the parties, which is forced to implement a large policy shift. We argue that a large policy shift may break a party internal balance among its different factions, which in turn may produce important disruptions in the party system. We illustrate our arguments with an analysis of recent events in Catalonia and the UK.