Electoral Competition in 2-Dimensional Ideology Space with Unidimensional Commitment

We study a model of political competition between two candidates with two orthogonal issues, where candidates are office motivated and committed to a particular position in one of the dimensions, while having the freedom to select (credibly) any position on the other dimension. We analyse two settings: a homogeneous one, where both candidates are committed to the same dimension and a heterogeneous one, where each candidate is committed to a different dimension. We characterise and give necessary and suffcient conditions for existence of convergent and divergent Nash equilibria for distributions with a non-empty and an empty core. We identify a special point in the ideology space which we call a strict median, existence of which is strictly related to existence of divergent Nash equilibria. A central conclusion of our analysis is that for divergent equilibria, strong extremism (or differentiation) seems to be an important equilibrium feature.