This paper considers an organizational aspect of the market in which votes are exchanged for public-policy outcomes. Specifically, the effect on the stability and behavior of politicians of assigning the demanders of political products (i.e., voters) to geographic areas is addressed. Implications concerning the locational division of the "buyers" of political outcomes for collusive efforts by existing officeholders to restrict entry are drawn and tested empirically. The results indicate in effect that the institutional structure of political markets is an important aspect of the degree of rivalry among existing politicians and hence the extent of entry by nonincumbent candidates.