This paper is an attempt to model the effect of economic changes in voting behavior through exploiting rational choice theory. In fact, I apply a modified version of Peter Diamond's two-periods overlapping generations model(OLG) to study voters' behavior in an election through extending his two periods model to a three periods model and endogenizing tax-rate in this model. This formal framework justifies a clear relationship between economic fluctuations and voters' behavior in elections. I show that economic shock has a signi cant e ect on election result from a rationalist point of view. Change in economic conditions causes change in individuals' income, and voting is a chance for them to react to these shocks in the economy through choosing the candidate who provides more utility for them. Empirical study in this paper manifests a significant relation between economic shocks and election result.