“…These groups are tied together by interaction (Truman 1951: 43) and, on the basis of shared attitudes, make claims upon other groups (Truman 1951: 33). As a result, they guarantee the system's stability (Truman 1951: 26-33; see also Zeitler 2006). These multiple memberships and the adherence to democratic rules of the game ensure that no group can promote its interest too aggressively.…”