Building on Key’s fundamental distinction and Katz’s and Mair’s modifications to this distinction, this chapter describes and analyzes the interaction of German voters and party elites at three distinct levels: the ‘party-in-the-electorate’, the ‘party-in-the-government’ (Key) or ‘party in public office’ (as Katz and Mair put it), and the party organization outside the legislature, particularly the ‘party on the ground’ (Katz and Mair). Our analysis focuses on individual parties and also covers the party system as ‘the system of interactions resulting from inter-party competition’ (Sartori 1976). We will aim to track important continuities in, and changes to, voting behaviour in respect of the main German parties individually and of the party system as a whole, concentrating on the period since unification in 1990. Drawing on a number of theoretical perspectives, including theories of electoral change, theories of organizational reform in political parties (in response to electoral change), and coalition politics at the governmental level, we will develop our argument as follows: after introducing the main parties and analyzing continuities and change in voting behaviour and party membership, we will analyze how political parties have responded to the growing levels of political uncertainty in organizational terms and will seek to address the seemingly paradoxical question why Germany’s party system has remained relatively stable at the governmental level (the party in public office), while parties in the electorate and parties as organizations have become far more fluid and vulnerable. (On the electoral system in Germany, including proportional representation and the statutory minimum of 5 per cent of the national vote a party must achieve to be represented in the Bundestag.