Political scientists have debated for some twenty years whether parties are in decline, losing their social anchorage, their hold on the electorate, their capacity to influence policy. Empirical evidence is manifold, pointing at, among other factors, declining party membership across modern democracies, increasing volatility and questionable policy impact (see, for example, Cotter and Bibby 1980; Daalder 1992; Dalton and Wattenberg 2000; Reiter 1989). Others have maintained that even though parties' erosion of social anchorage is hardly questionable, this does not amount to party decline across the board because, by and large, parties have been able to compensate for this loss by turning to the state (Katz and Mair 1995). Parties have, however, not responded to these challenges merely by looking for alternative sources of organizational strength, namely state resources. They have also responded to their changing social environment in a number of ways which will be discussed in the present volume. Rather than considering themselves merely as objects of wider social change, parties - better: party elites - have retaken the initiative and have attempted to change the patterns of interaction with their own membership organizations and their wider social environment in ways more compatible with the social realities at the beginning of the twenty-first century. In a nutshell, their reactions to these challenges have significantly transformed the way parties respond to their voters. Trying to adapt to an increasingly fragmented social environment and deprived of formerly stable anchorage in society, parties may have changed from aggregating interests to merely 'collecting' them, thereby relying ever more on modern communication and market research techniques. Before we turn to discussing exactly how parties have changed their modes of responding to their electorates, however, let us briefly reflect on the nature of the challenges that have confronted parties over the past decades.
Most of them are related to the dramatically increased social complexity of modern societies. Otto Kirchheimer argued (1966) that the success of