Pakistan has announced a date for an election for a new president.
The election commission says it will be held on 6 September. The Pakistan People's Party, which Asif Ali Zardari leads, said he will contest the election.
The poll is to select a successor to Pervez Musharraf, who resigned this week to avoid impeachment charges.
Hours after the announcement, Mr Zardari, was unanimously nominated to stand for the Pakistan People's Party. Ms Bhutto was assassinated in a suicide attack in December.
The PPP and PML-N have been discussing ways to reduce the power of the presidency, but if Mr Zardari gets the job, it is not clear if such reforms will go ahead.
Nawaz Sharif, leader of the PML-N, prefers what he calls a consensus president.
The PPP is embroiled in a dispute with Nawaz Sharif, another ex-prime minister, over the reinstatement of judges who were deposed under a state of emergency last year.
The fate of the 60 judges, including the chief justice, is a political sticking point with crucial repercussions for the coalition.
Suicide bomber kills policemen
Pakistani police reported on Saturday that a suicide bomber killed at least eight policemen and injured several others in north-western Pakistan's Swat Valley.
The bomber drove a vehicle laden with explosives at a checkpoint in an attack claimed by an Islamic militant group, Tehrik-e-Taleban Pakistan.
The same group claimed an attack on a Pakistani munitions factory last week which killed at least 63 people, the BBC reports.
Militants killed in Swat Valley
Pakistani troops killed 35 militants in fighting in the Swat Valley northwest of Islamabad on Saturday after the militants ambushed a patrol, a military official said.
Four soldiers were also killed, said the official. The fighting erupted shortly after a suicide bomber rammed a vehicle into a police station in another part of the valley, killing eight policemen.
Nuclear-armed Pakistan is on the front line of the United States-led war against terrorism and al Qaeda-linked militants have unleashed a wave of violence across the country over the past year against the security forces.