Although it sounds like something from the SCUM Manifesto
( I have seen the future, the future is cleavage!), Political cleavage refers to the situation in a bipartite political system where political allegiances are drawn along class lines. US political sociologist Seymour Lipset sees political cleavage within democratic systems as the key explanatory variable for their ongoing stability - as long as both parties play by the rules of the game, bloody revolutions can be avoided.
The emergence of political cleavages has been identified
either as a result of the political mobilisation of sectors of society affected by national and industrial revolutions, or because individuals inherently identify with particular social groups, which are then used as markers by political parties to mobilise support. Cleavages first occured during the formative years of democracies and have persisted since.
When you grow up, do you want to be a radical American political sociologist? see Lipset, Seymour M., & Rokkan, Stein. (1967). Party systems and voters alignments. New York: Free Press, for all your cleavage needs.