The concept that voters in Western liberal democracies, who were formerly aligned into well‐defined social groups on the basis of commonalities such as class, religion, and ethnicity, and exhibited high partisan identification as a result, have over time become more loosely attached to such allegiances and have more aleatory and fleeting preferences in electoral competition. The concept is opposed to that of realignment, in which voters lose attachments to prior allegiances but instead gain new ones, and a distinction is usual between social dealignments and partisan dealignments.
The concept of dealignment became widespread during the 1980s, and three major causes can be identified. First, some writers observed an apparent general weakening of social and political group identities in Western societies, evidenced by, for example, falling labour union membership, political party membership, and religious observance, and this was associated with the rise of cross‐group identities and consciousness found by sociological works such as John Goldthorpe's ‘Affluent Worker’ studies in the UK. Simple ideas of voter alignment seemed ill‐suited to rising social complexity, and were sometimes linked to materialist conceptions of politics equally ill‐suited to represent the rise of new issues identified in Ronald Inglehart's post‐materialism thesis. Secondly, in the US, the temporal pattern of realignments at critical elections appeared to have been broken, with no clear new alignment arising from the partial disintegration of the New Deal coalition. Thirdly, rational choice models of behaviour, which had become increasingly popular, implied a consumerist model of voting in which choice rather than identity was crucial.
However, the extent of dealignment has been strongly contested: levels of party identification have ceased to fall in the US, and the extent and meaning of class dealignment in UK voting is the subject of a lengthy and vigorous dispute. See also critical elections.