Uncertainty of voters' preferences and differentiation in a runoff system

Haan and Volkerink (Haan, M., Volkerink, B., 2001. A runoff system restores the principle of minimum differentiation. European Journal of Political Economy 17, 157-162, this journal) show that the principle of minimum differentiation holds in two-round elections for any number of candidates. We show that the principle of minimum differentiation may not hold, when uncertainty of the position of the median voter is introduced.