Scholarly interest in the relationship between social cleavages and political alignments can be traced to recurring political predictions (especially in the European context) that the interests of a growing working class might provide the foundation for an 'electoral road to socialism'. These predictions were based on the assumption that class interests inevitably lead voters to favor the political party most likely to advance those interests. The 'class politics' thesis became the object of social science inquiry when political change did not unfold in the ways predicted by the theories put forward by Marxists and other social democratic intellectuals.
The implications of extending the franchise to the working class in late nineteenth-century Europe were widely debated. In the infamous introduction to the 1895 edition of Marx The Class Struggles in France, 1848-50, published at the very end of his life, Friedrich Engels hailed the steady growth in the votes received by the German Social Democratic Party (SPD), arguing that this signaled the inevitable electoral triumph of socialism. Engels wrote that 'the two million voters [the SPD] sends to the ballot box . . . form the most numerous, most compact mass, the decisive "shock force" of the international proletarian army. This mass already supplies over a fourth of the votes cast; and . . . [i]ts growth proceeds as spontaneously, as steadily, as irresistibly, and at the same time as tranquilly as a natural process. All government intervention has proved powerless against it.' 1 Conservative opponents of the socialist movement were also keenly interested in the political effects of the extension of the franchise. For example, in the debates in Britain in the 1860s over reform proposals to extend the franchise to all male voters--irrespective of their property endowment--one of the bitterest opponents of the pending legislation, a Conservative member of Parliament, Robert Lowe, declared:
Look at this tremendous machinery: if you only arm it with the one thing it wants--the Parliamentary vote . . . the working classes . . . are the lever. But