This dissertation investigates the drivers behind political decision-making and the policy outcomes resulting from political decisions. It is proposed that in policy processes where political decisions are made at multiple levels or across multiple policy subsystems, policy outcomes can be understood in terms of the mechanisms (i.e. the processes or means) of interaction between multiple policy subsystems within which political decisions are made,resulting in more or less policy alignment between political decisions and policy outcomes. Policy network theory and policy subsystem theory are used separately as the basis forderiving two potential explanations for the mechanics of policy subsystem interactions. Because political decision-making authority in the wind power policy process in most Western democratic countries is spread across multiple policy subsystems, and because there has been significant variation between wind power policy outcomes between these countries, wind power policy processes in European Union countries are used as an empirical point-of-departure for exploring and illustrating the mechanics of policy subsystem interaction. A survey of the research on wind power development is used to illustrate and explore preliminary empirical indications of support for a framework derived from policy network theory. The case of political decisions made in Sweden over the past twenty years related to wind power development and production is used to illustrate and explore preliminary empirical indications of support for an explanation of policy subsystem interactions derived from the Advocacy Coalition Framework proposed here, as well as to explore the drivers of political decisions. This dissertation therefore contributes to understanding how policy subsystems interact. The dissertation contributes theoretically to the literature on policy processes generally, as well as to network/network management theory, and to the Advocacy Coalition Framework/policy subsystem theory. It also contributes to understanding two strategically chosen, embedded cases within the broader case study of political decision-making in the wind power policy process in Sweden.