How sensitive do voters react to policy positions of parties in multiparty systems and which implications do the voters policy reactions have for the parties to be reelected? By transferring approaches originally developed in transportation economics and marketing sciences to political science, the book tries to systematically answer these questions. It reformulates the spatial theory of voting in terms of stochastic multiattributive decision theory and uses features of candidates and parties as decision criteria. By taking advantage of statistically innovative tools, empirical policy reaction functions are estimated for the first All-German election in 1990.