The Effect of Ministerial Instability on Government's Mandate Fulfilment: Evidence from the Portuguese Case

Research on the fulfilment of electoral promises has been particularly fruitful over the past decades. Most of it focused on examining pledge fulfilment at the cabinet level, and little emphasis was placed on the reasons underlying the level of compliance. As a consequence, core factors in explaining pledge fulfilment have not yet been explored. One such factor might be instability in a government's internal functioning. We argue that ministerial instability is relevant for explaining a government's broken promises, and that its importance increases at the junior minister level and among the most salient ministries. Relying on data on the fulfilment of electoral promises and ministerial instability in Portugal between 1995 and 2019, backed by interviews with former ministers and junior ministers, we provide evidence that the fulfilment of electoral promises is significantly influenced by portfolio volatility, particularly at the junior ministerial level and in the most important ministries.