Spatial theory is divided between models of elections and models of roll call voting, neither of which alone can explain congressional polarization. This chapter discusses the history of spatial theory, why it is important to link the two strands of spatial models, and the value of reversing the order of conventional models. Conventional models place an election before policy decisions are made. This chapter proposes a unified spatial model of Congress in which the conventional order is reversed. First, there is a legislative session, then an election in which voters respond retrospectively, not to the locations candidates claim to hold, but to the bundles of roll call votes that incumbents cast to incrementally adopt their locations in the policy space. Such a model is best suited to explaining three puzzles: why do legislators adopt extreme positions, how do they win, and what role do parties play in the process?
Spatial modelling of risk premiums for water damage insurance