This article illuminates the relationship between the increased importance management has gained in public institutions, and political reality in everyday work lives. It attempts to gauge the rationalities behind the managerial and the political system and derives a heuristic structure from them. On the basis of this discussion, an analysis is conducted of the origins of new public management, using Switzerland as an example. It is concluded that NPM reforms started as managerial reforms of public institutions, but that they developed into de facto political reforms. Thus the managerial background of project managers, consultants and public management scholars is a necessary but not sufficient precondition for a successful implementation of NPM in the politico-administrative system. The contribution which public management is able to make to the governance debate must not be underestimated. Not least, it leads to a clarification of the sources of legitimacy of government action. The rationality model introduced in this article is designed to make systemic differences between management and politics visible - and to improve communication between politicians and public managers.