This article proposes a general model of partisan political dealignment based on the theory of expressive voting. It is based on the Riker and Odershook equation. Voters cast a ballot for a political party if the utility associated with expressing their support for it is more than their expressive costs. Expressive utility is modeled here as a certain utility model. Then, the model is applied to the rise of voting support in favor of French right-wing populists, the National Front (FN). We show that the fall of justification costs of FN ideology along with the decline in stigmatization costs of voting in favor of the extreme right has fostered the popularity of this party. Political dealignment here is only a particular case of a general process of political norms transgression inherited by each voter.