This article investigates to what extent social democratic parties still benefit from the support of union members at the polls. Not only are social democratic parties confronted with new competitors in the party systems, but also the union confederations of the socialist labour movement are in some countries losing their dominant position due to the rise of separate professional confederations. It is argued in the article that the effect of union membership on voting choice is conditioned by the structure of the trade union movement. The support of union members for social democracy is fostered by the strength of the confederations historically close to this party family, while it is hampered when strong separate (or politically unaffiliated) white‐collar confederations exist. Using European Social Survey and Swedish Public Opinion data, the article shows that social democratic parties still enjoy important support from trade union members, but at the same time are under fierce competition from bourgeois and green parties among members of white‐collar confederations. This reinforces the challenges for social democracy to build new voters’ coalitions in post‐industrial societies.

The rise of the radical right fundamentally changes the face of electoral competition in Western Europe. Bipolar competition is becoming tripolar, as the two dominant party poles of the twentieth century – the left and the centre‐right – are challenged by a third pole of the radical right. Between 2000 and 2015, the radical right has secured more than 12 per cent of the vote in over ten Western European countries. This article shows how electoral competition between the three party poles plays out at the micro level of social classes. It presents a model of class voting that distinguishes between classes that are a party's preserve, classes that are contested strongholds of two parties and classes over which there is an open competition. Using seven rounds of the European Social Survey, it shows that sociocultural professionals form the party preserve of the left, and large employers and managers the preserve of the centre‐right. However, the radical right competes with the centre‐right for the votes of small business owners, and it challenges the left over its working‐class stronghold. These two contested strongholds attest to the co‐existence of old and new patterns of class voting. Old patterns are structured by an economic conflict: Production workers vote for the left and small business owners for the centre‐right based on their economic attitudes. In contrast, new patterns are linked to the rise of the radical right and structured by a cultural conflict.

Relying on post-election surveys, we analyze how class and union membership condition voters’ abandonment of mainstream Left parties and the alternatives chosen by former mainstream-Left voters in the period 2001–2015. Inspired by Przeworski and Sprague’s Paper Stones (1986), our analysis shows that Left parties face a trade-off between mobilizing workers and other voters and that unionization renders workers more loyal to Left parties that mobilize non-workers. By contrast, unionization does not render non-workers more loyal to Left parties that mobilize workers. Union membership increases the likelihood that workers who abandon the mainstream Left continue to vote. It also increases the likelihood that voters abandon the mainstream Left in favor of radical Left parties rather than Center-Right parties. Finally, we show that workers are more likely to abandon mainstream Left parties in favor of radical Right parties than non-workers and that union membership does not affect their propensity to do so. We conclude that reversing the decline of working-class organization should be a long-term objective of mainstream Left parties.