Electoral volatility: Issue effects and basic change in 23 post-war democracies

Growing differences between party votes in successive elections have raised the possibility that party systems are undergoing fundamental change. This cannot be settled until aggregate vote differences are separated into those normally produced by new issues and candidates, and those reflecting an erosion of core support. A saliency theory of party competition and electoral response is used to quantify net shifts in voting produced by issues identified on the basis of campaign reports. Estimates are validated by comparison with others produced on different assumptions and through their success in predicting election results in ten countries. By ‘controlling’ these issue effects we can estimate Basic Votes for each party and election and see whether they have changed.