The declining association between occupational class and political alignment in Britain has now been documented by a number of studies. For the political analyst the decline of a previously important cleavage must raise complex questions of causation. One of the most important possible explanations for such a change is that a new cleavage has arisen or grown in political significance so that its influence on political alignment cross-cuts that of the previous cleavage, blurring its impact and exposing sections of the population to contradictory or cross-pressuring influences. But political commentators in present-day Britain have apparently ruled this out as an explanation of the declining electoral influence of occupational class. Crewe, for example, remarks:
It is difficult to think of any social cleavages or fundamental changes in the social structure in the last twenty years that could have affected national partisan alignments in any way comparable to the substitution of the religious cleavage by the class cleavage in the first three decades of this century. Glacially slow changes in the British social structure have undoubtedly taken place. The emergence of coloured immigrant communities, the growth of white collar employment (and of white collar ‘trade unionism’), the movement of agricultural workers to the towns and their displacement by commuters and the retired rich, a further secularization and a growing disparity of income between the organized and unorganized working class are all cases in point. But in all these cases, shifts in party support have been small, often only temporary, and always localized; no shift in the social structure has produced an enduring, nationwide realignment of party support since 1945.