Political parties are the building blocks of representative democracy since they traditionally perform roles that are considered essential for the functioning and well-being of democracy. In the study and evaluation of the democratic system as a whole, as a general rule, parties are treated as unitary actors. Most political parties, however, are membership organizations and their external functioning is partly dependent on internal affairs, including the behavior and opinions of their members. In this paper we open the black box of parties and show on the basis of a 2008 survey among seven political parties how united or divided ordinary Dutch party members are with respect to various political issues and orientations. It is shown that most parties are rather united on most issues. They are least united on two of the most pertinent issues of today’s politics, i.e. the integration of ethnic minorities and European integration.