Article published on the 2008-08-31 Latest update 2008-08-31 14:12 TU
The PPP has the largest number of members of the National Assembly and two of the four provincial bodies.
But that hasn't deterred the Muslim League of former Prime Minister Nawaz Sharif (PML-N) from standing retired chief judge Saeed uz Zaman Siddiqui. The party has split from the ruling coalition over the PPP's failure to reinstate judges sacked by Musharraf last year.
The party which split from Sharif to back Musharraf, the PML-Q, is standing former government official and journalist, Mushahid Hussein. Musharraf resigned on 18 August after the PML-N and the PPP threatened to impeach him.
Zardari is returning to politics after accompanying his wife back to Pakistan from exile. Before that he spent 11 years in jail on corruption and other criminal charges. On Tuesday Swiss prosecutors shelved charges of money-laundering against him for lack of proof and unfroze bank accounts holding 40 million euros.