Since the heyday of cleavage voting in the 1960s and 1970s, the majority of studies presents evidence of a decline in cleavage voting - caused by either structural or behavioural dealignment. Structural dealignment denotes changes in group size responsible for a decrease in cleavage voting, whereas behavioural dealignment concerns weakening party-voter links over time. A third phenomenon posited in this article is the collective voting abstention of certain (social) groups, here referred to as 'political dealignment', which results in a new type of division of voting versus abstention. The purpose of this article is to examine the three underlying mechanisms for the decline in social class and religious cleavage voting across four Western countries (Great Britain, the Netherlands, Switzerland and the United States) over the last 40-60 years using longitudinal post-election data. The results prove a strong presence of political dealignment and increasing turnout gaps regarding both the class and religious cleavage. Furthermore, whenever a decline in cleavage voting is present, it is mainly caused by changes in the social groups' behaviour and less by changing social structures in a country.