Mushahid Hussain is a senator for the Pakistan Muslim League Q, the party which staunchly supported Musharraf.
"It will be an easy victory for Asif Ali Zardari as we have the support of more than 400 lawmakers out of about 700," Farhatullah Babar, a spokesman for the PPP, said.
The next president of Pakistan will have to face a myriad of problems plaguing the country, including its economic malaise and increasing violence in the north.
On the eve of the election, Pakistani officials reported five people had been killed in a US air raid in North Waziristan province, the second in 24 hours.
"We stand with the United States, Britain, Spain and others who have been attacked"
Asif Ali Zardari, co-chairman of the Pakistan Peoples Party
At least five people were reported to have been killed by missiles from an unmanned drone on Friday, with different sources referring to them as either fighters or civilians.
A suspected US drone missile had also killed four people near the area a day earlier.
Pakistan had summoned the US ambassador on Wednesday to protest against the killing of 20 people by US commandos from across the border in Afghanistan.
Unrest in the northwest has been attributed to tribal anger at Musharraf's support for the US "war on terror".
Bombings and suicide attacks have killed nearly 1,200 people across Pakistan in the past year alone.
Musharraf's resignation triggered Saturday's election but his military policy is likely to continue with Zardari.
The 53-year-old presidential hopeful has said that Pakistan will continue to back the US if he is elected.
"I will work to defeat the domestic Taliban insurgency and to ensure that Pakistani territory is not used to launch terrorist attacks on our neighbours or on Nato forces in Afghanistan," he said in a Washington Post article.
"We stand with the United States, Britain, Spain and others who have been attacked."
Besides the violence, Pakistan's new president will have to work to turn around a faltering economy.
Rampant inflation and an unstable political situation have contributed to a 40 per cent fall on the stock market since January.
Islamabad is already heavily dependent on the billions of dollars of aid sent from Washington since Musharraf backed the US invasion of Afghanistan after the September 11 attacks in 2001.