‘Moves on a Chess Board’: A Spatial Model of British Prime Ministers' Powers over Cabinet Formation

We use an institutional rational choice approach to help us understand how prime ministers in the UK make cabinet appointments and the implications for prime ministerial power. Assuming that prime ministers attempt to form a cabinet so as to get an overall package of policies as close as possible to their ideal, we show why the trade-offs they face are so complex, why apparently common-sense rules for making appointments might not always work well and why apparently strange choices made by prime ministers might actually be rational. Acknowledging the power prime ministers derive from their ability to appoint, we argue that the literature commonly fails to distinguish between power and luck, where lucky prime ministers get their way because they happen to agree with colleagues.