Although Musharraf is not up for re-election, he could face impeachment if the opposition wins a two-thirds majority in the legislature.
On Thursday, Musharraf advised opposition parties not to immediately claim election fraud and stage demonstrations after the vote.
The message was underlined by Mohammedmian Soomro, the caretaker prime minister, who said there would be "zero" tolerance for efforts to disrupt the election.
Another opposition party, headed by Nawaz Sharif, the former prime minister, rejected Musharraf's warning, saying it would stage nationwide protests if it believes the election was manipulated.
"We know Musharraf wants to rig the elections," said Sadiq ul-Farooq, a senior member of Sharif's party.
"If he did it, we will force him to quit through street protests."
Yet another politician, Qazi Hussein Ahmed, the leader of Jamaat-e-Islami, told Al Jazeera that his group would stage demonstrations against Musharraf in protest against his warning.
On Thursday, Musharraf insisted the elections would be free and fair, but strongly criticised recent opinion polls by US groups that indicated the opposition parties were headed for landslide victory.
A survey released this week by the US government-funded International Republican Institute said half the Pakistanis polled planned to vote for Bhutto's party and 22 per cent backed Sharif's party.
The poll, conducted on January 19-29, showed that only 14 per cent of the 3,845 adults polled favoured Musharraf's ruling PML-Q.
Candidates have resorted to door-to-door campaigning to drum up support or hanging banners along roadsides, though momentum has picked up in recent days.
The December 27 assassination of Benazir Bhutto and a string of recent suicide bombings have discouraged many candidates from holding large rallies.
Bhutto killing arrests
On Friday, a fifth arrest was made over the assassination of Bhutto.
Abdur Rashid was taken into custody in Kamra, a town near the capital Islamabad, the head of the investigation Chaudhry Abdul Majeed said.
Rashid appeared in a court in Rawalpindi where he recorded a statement admitting to have assisted those who carried out the December 27 attack, Abdul Majeed said.
|Security has been stepped up and rallies kept to |
a minimum after Bhutto's assassination [AFP]
Rashid comes from the North West Frontier Province, where pro-Taliban groups have been battling Pakistani government forces.
On Wednesday, police had announced that two Pakistanis, Husnain Gul and his cousin, had confessed to helping two assassins, one of whom died in the suicide attack.
Two others, including a 15-year-old boy, have also been arrested in relation to Bhutto's killing.
The developments come against a backdrop of rising tensions, particularly in northwestern Pakistan.
On Thursday, suspected Taliban fighters attacked a military post near Dera Adam Khel, killing one paramilitary soldier and wounding another, an army statement said.
Tens of thousands of soldiers are on alert to provide security for Monday's vote.