The Duvergerian theory has been used to explain the behaviour of both party elites and voters. Through the mechanical and the psychological effects of the electoral laws political parties are supposed to withdraw from competition in the long term when nonviable. When parties fail to anticipate these mechanisms, voters will be encouraged to desert this party. In the long run one would expect only viable parties to concur elections. However, this has been shown not to be true. Nonviable political parties continue presenting candidates, calling into question the Duvergerian theories. Departing from the unexplained paradox that more parties than those that are expected to run for election decide to compete, this paper argues that it is the superposition of more than one electoral arena or district that encourages viable parties to present candidacies in those districts where they are nonviable.

Keywords: Duvergerian gravity, asymmetric viability, electoral contamination, externality.