Between 1999 and 2009, since no single party was in a position to lead a majority in the Lok Sabha, pre-electoral coalitions have become the only option for parties to exercise executive power at the Centre. Looking at the trajectory of two pre-electoral coalitions over ten years, namely the BJP-led National Democratic Alliance and the Congress-led United Progressive Alliance, the paper attempts to contribute to the nascent research on pre-electoral coalitions. Much has been written on the importance of disproportionate electoral systems or the ideological distance between parties in the formation of governing coalitions. This paper explores the importance of different geographical bases of support in the composition and sustainability of Indian pre-electoral coalitions, election after election, and proposes preliminary elements for a dynamic theory of pre-electoral coalition formation.