European social democratic parties have lost massive vote shares over the past twenty years. However, their electoral potential – that is, the number of voters who include the social democratic party in their consideration set – is still very high, at about 40–50% on average.

In this chapter, I use EES data on individual voting propensities from 2004 to 2019 in ten countries of Continental, Nordic, and Southern Europe to compare electoral potentials, overlaps with rival party electorates, as well as the sociodemographic profile of voters who are part of inward or outward overlaps between social democratic parties and their rivals.

I find that overlaps are highest within the left field, especially between green/left-libertarian and the social democratic electorates: About 50% of social democratic and green voters could also imagine voting for the other party, compared to only 10–20% between the social democratic and radical right parties. Moreover, the majorities of inward and outward overlaps – especially within the left field – concentrate among middle-class voters with medium or high levels of education.

The last section of the analyses compares in- and outward overlaps and discusses them in relation to the four programmatic strategies developed in this book. In relative terms, I find the New Left strategy to be the one for which potential electoral gains from green and left-libertarian parties seem both highest, as well as most realistic, compared to on average very low potential losses to the Right, in particular to the Radical Right. Overall, however, outward overlaps are systematically higher than inward overlaps for social democratic parties.