Since the 1970s, Pakistan's politics had basically been defined by a polar struggle between a political block centered around the Pakistan's People Party (PPP) established by Zulfikar Ali Bhutto, and a block of anti-PPP forces, generally led by the Pakistan Muslim League (PML) under the leadership of Nawaz Sharif. While the organizational forms of this confrontation varied as did the cohesion of both camps, it still remained the key line of conflict in Pakistani politics. At the same time, the armed forces (especially the Army) always remained a key political actor, sometimes in the background, sometimes very much at the forefront. This polarized system of political confrontation, with the army looking over the shoulders of politicians, strongly impeded the development and stability of democracy in Pakistan. Two opposing poles of politics accusing each other to be enemies and even "traitors" of Pakistan made cooperation between the parties extremely difficult. Jointly serving the country to solve its many problems became nearly impossible. Democracy, though, requires not just fair elections and peaceful change of governments, but also a functioning mix of control and critique of the government by the opposition, and forms of mutual respect and cooperation. The polarization of politics undercut democratic rule by making such a balance impossible. It should have been no surprise therefore that for well into the 21st century no government could peacefully complete its tenure, but all were overthrown either by a coup, or by the abuse of the constitution by civilian Presidents, or the courts.