Book excerpt: The central concern of Understanding Political Change is to explore the social and political sources of electoral change in Britain. From the Labour successes of the 1960s through the reemergence of the Liberals as a national force in 1974 and the rise and fall of the SDP to the potential emergence of the Green Party in the 1990s, Dr Heath and his collaborators chart the continually changing mould of British politics. Questions of the greater volatility of a more sophisticated electorate, of new cleavages in society replacing those based on social class, of the Conservative government's deliberate and inadvertent interventions to shape the emerging social structure, and of the influence which the political parties have been able to exert on public attitudes are all addressed with reference to data from the election surveys carried out after each general election since 1964.