The Illusion of Electoral Stability: From Party System Erosion to Right-Wing Populism in Brazil

Although comparative research has relied heavily on electoral volatility as a proxy for party system institutionalisation (PSI), this measure cannot account for the patterns of interparty interactions that are key to determine the degree of party system stability. I develop a new measure – the party bloc volatility (PBV) index – to account for consistency in the ideological positions and in the partisan composition of the government and opposition blocs. I demonstrate the limitations of the index of electoral volatility by analysing the case of Brazil. Although electoral volatility substantially decreased between 1994 and 2010, the patterns of interparty alliances became less and less predictable from 2002 onwards, as party fragmentation increased while interparty ideological differences decreased. In combination with a major economic and political crisis, these trends led to the discrediting of the established parties and thus favoured the rise of the extreme right in the 2018 elections.