This study documents the changing structure of Pakistan's political cleavages by making use of a unique set of exit polls covering every direct election held in the country between 1970 and 2018. We analyze the evolution of the party system, beginning with the initial economic "left-right" opposition between the Pakistan Peoples Party (PPP) and the Muslim Leage. Regionalist, ethnolinguistic and religious divides have weakened and transformed this party system. The decline of the PPP has come with its transformation from a lowincome mass-based party to an ethnic party confined to Sindhi speakers. We also analyze the recent rise of the Pakistan Tehreek-e-Insaf and the role played by the political unification of the various economic, religious and military elites in its success. Finally, we discuss how the Islamization policies implemented under the military regime of Zia-ul-Haq (1977-1988) have contributed to weaken the development of a pro-redistribution secularist coalition.