Updated

A major opposition party on Wednesday backed Benazir Bhutto's widower to become Pakistan's president, as the power struggle following the resignation of Pervez Musharraf intensified.

Asif Ali Zardari leads the largest party in the ruling coalition, whose drive to impeach Musharraf persuaded the stalwart U.S. ally to quit after nine tumultuous years in power.

Zardari has played down speculation that he covets the top job.

However, opposition backing will strengthen his hand in a struggle with coalition partner Nawaz Sharif over a compromise candidate to fill the post and the even more urgent issue of restoring judges purged by the former army strongman.

A leader of the Muttahida Qaumi Movement, Haider Razvi, said it wanted Zardari as president because of his past sacrifices and for his "wisdom and vision" in handling Musharraf's ouster.

The MQM, a strong backer of Musharraf, is the second-largest opposition group in Parliament.

It dominates Karachi, Pakistan's biggest city, and other urban areas in the southern province of Sindh and recently buried its long animosity with Zardari's Pakistan People's Party.

Razvi called for a president from outside Punjab, the country's largest and wealthiest province, and said Zardari — a Sindhi — was "most eligible" for the job.

"He is a strong believer in the federation," Razvi said.

The coalition began wrangling over the fate of Supreme Court judges ousted when Musharraf imposed emergency rule last year, just a day after his resignation.

Sharif, whose government was ousted when Musharraf seized power in a military coup in 1999, has championed their cause and wants them returned immediately.

The judges could prove useful allies if Sharif tries to make good on a threat to have Musharraf tried for treason — a charge punishable by death.

However, Zardari has consistently linked their restoration to constitutional amendments that could limit their powers and ultimately protect the ex-general.

Talks on the issue Tuesday produced no breakthrough, exposing a rift that could sink the coalition. Sharif lieutenants say they want a deal by Friday.

"The future of the coalition government is linked to the restoration of all judges sacked by Musharraf," said Sadiqul Farooq, a spokesman for Sharif's party.

If they clear that hurdle, the parties must also seek agreement on a candidate for the presidency — which in the future will likely be stripped of its power. People's Party officials have said it should be a member of their party.

They have yet to name a candidate for an election by lawmakers, which must take place by mid-September.

However, Zardari has suggested it should be a woman, catapulting parliament speaker Fehmida Mirza — a ringer for his late wife — into the speculative running.

Sharif has told Zardari that the president should be from the impoverished western province of Baluchistan, rather than from larger Punjab or Sindh, Farooq said.

Attaullah Mengal, a tribal chief and veteran Baluch nationalist has also been touted in the media.

The main opposition bloc, the Pakistan Muslim League-Q, said it would wait for the coalition to come up with a candidate before deciding whether to field their own.

Few analysts expect the coalition to collapse, arguing that Sharif and Zardari need to share the burden of tackling Islamic militancy and serious economic problems.

However, if it does, Zardari's party could look to the MQM and even elements within the Pakistan Muslim League-Q, Musharraf's main prop, to shore up the government.