Is it not obvious? There are many reasons but here are few: Throughout coalition period PPP wanted PMLN to run Punjab as coalition partner but PMLN wanted to run the show alone. PMLN was ruling Punjab with the help of PPP MPA votes but was not recognising those votes. Throughout PMLN was talking not only bad about PPP leadership, but were harassing PPP workers and voters in Punjab. Actually, PMLN were doing corruption in big way and abusing power in Punjab, and were harassing and victimising members of every political party in Punjab, including PPP and PMLQ (when PPP wanted to create new environment of conciliation in Pakistan).
Are there any news items to back these accusations of harassing PPP workers, voters, abusing power, victimising members of every political party etc? or were you living there and are evidence to it?