Abstract
This paper analyzes the different compositions of the Catalan governing coalitions during the current democratic period, and offers some predictions about the coalitions that can be expected in the future. During this period, in catalan politics, there have been two main political issues over which the different parties have taken positions: rightist versus leftist with respect to economic policy, and sovereign versus centralist with respect to the power distribution within the state. We find that for any allocation of parliament seats there is a key party: a party that has a clear advantage in terms of being able to decide the composition of the governing coalition. We show the features that allow a party to become the key party and those that affect the size of the advantage of the key party.