Party policy equilibrium for alternative spatial voting models: An application to the Norwegian storting

In recent years a lively debate has emerged concerning the empirical status of the traditional proximity spatial model versus a directional model of voter choice. The central reason for this scholarly interest concerns these models' contrasting implications for parties' policy positioning, with the directional model motivating parties to present extreme policies, but the proximity model promoting centrist positions. To this point, however, there exist no studies that compute parties' optimal strategies in historical elections, for these competing models. This article addresses this issue, by examining party policy strategies in a multiparty electorate for three different vote models: (a) the proximity model, (b) a directional model (c) a mixed model which combines proximity and directional components. Each model incorporates past voting history and the random effects of unmeasured variables. Using parameter estimates derived from analyses of survey data from the 1989 Norwegian Election Study we compute — for each of these vote models — the configuration of party policy positions that maximize each party's vote share in relation to those of the other parties. We find that for each model, such a vote–maximizing configuration exists, but — for the proximity model — represents an unrealistic, tightly clustered array. A mixed proximity–directional model, however, provides by far the most convincing account of parties' actual policy strategies with regard to dispersion and vote share.