Musharraf's popularity has slumped since he tried to dismiss the chief justice in March and imposed six weeks of emergency rule in November, and he could face new challenges to his power if his opponents dominate a new parliament.
Some Pakistanis believe the government might again postpone the election citing deteriorating security.
"There's uncertainty after the assassination of Benazir and a worsening law and order situation. Nobody is sure whether the election will be held or not," said Abdul Aziz, who owns a printing press in the eastern city of Lahore.
Violence has been spreading from remote tribal areas on the Afghan border to cities and towns across Pakistan and hundreds of people have been killed in recent months.
Ahsan Iqbal, a spokesman for the opposition party of former prime minister Nawaz Sharif, said the government was playing up the security fears to stymie opposition campaigns.
"They know that their allies are weak," he said.
Sharif said last week poor security was hindering campaigning. Shortly afterwards police in the city of Peshawar defused a bomb along a route he was about to take.
Raja Pervez Ashraf, secretary general of Bhutto's Pakistan People's Party, said the party was still in a state of shock.
But he said Bhutto's husband and a new co-chairman of he party, Asif Ali Zardari, would step up the campaign at the end of a 40-day period of mourning for her on February 7.
"We are carrying on the campaign in constituencies but there is a great sense of insecurity among the people," Ashraf said.
Fazl-ur-Rehman, head of the largest Islamic party, the Jamiat-e-ulema-e-Islam, is visiting Saudi Arabia. The government has identified him as being under threat from militants.
Nawab Khan, an activist for an ethnic-Pashtun party in Peshawar, said he was struggling to drum up public interest.
"There's no enthusiasm," said Khan in his election office.
"A man would prefer to stand in a queue to get few kilograms of atta (wheat flour) than queuing up outside a polling station and get himself killed in a suicide attack."
