Why the left has more to lose from ideological convergence than the right

Abstract

Why are many traditional governing parties of advanced democracies in decline? One explanation relates to public perceptions about mainstream party convergence. Voters think that the centre-left and -right are increasingly similar and this both reduces mainstream partisan loyalties and makes room for more radical challengers. Replicating and extending earlier studies, we provide evidence supporting this view. First, observational analysis of large cross-national surveys shows that people who place major parties closer together ideologically are less likely to be mainstream partisans, even when holding constant their own ideological proximity to their party. Second, a survey experiment in Germany suggests that this relationship is causal: exposure to information about policy convergence makes mainstream partisan attachments weaker. Importantly, we advance previous discussions of the convergence theory by showing that, in both our studies, ideological depolarisation is most detrimental to mainstream centre-left partisan attachments. We suggest that this is due to differing party histories.