Less than a year ago Asif Ali Zardari appeared to be yesterday's man. Seemingly sidelined by his wife, Benazir Bhutto, and her party, facing a series of corruption charges and bearing the nickname "Mr 10 Per Cent", it appeared that his days of power and influence were over.

Now he is back, as never before. Having been catapulted to the forefront of Pakistan's political maelstrom by the assassination of his wife, Mr Zardari is poised to become his country's head of state. At the end of a remarkable week which saw Pervez Musharraf (inset) resign as president to avoid impeachment, the Pakistan People's Party (PPP) announced that its chosen candidate to replace him would be Mr Zardari.

The man who spent 11 years in jail over corruption charges he claims were politically motivated, yesterday confirmed he would take the post. It would have been remarkable if the party he has led since his wife's death last December had not agreed to nominate him. Yesterday PPP officials were meeting with coalition partner Nawaz Sharif to try to secure his backing for the nomination. "We want a joint candidate for the race," said PPP spokesman Jameel Soomro.

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February's parliamentary elections saw the PPP secure most seats and Mr Zardari has become increasingly powerful by dint of his leadership of the party, gifted jointly to him and his son, Bilawal, by Ms Bhutto in her will. With Mr Musharraf much weakened, Mr Zardari has acted as de facto prime minister, and hand-picked senior appointments.

Subsequently, the centre of political power in the capital has shifted to a leafy street in a quiet neighbourhood. On a side street, past layers of barbed wire, concrete blocks, metal detectors and barriers, lies Zardari House. It is here, some miles from the row of Islamabad's ornate government buildings, that key decisions are now made.

Each day, the home attracts a steady stream of visitors. Outside the gates, the media gathers behind a phalanx of television cameras. In front, a steady queue of courtiers and supplicants arrives to be searched and vetted before they jostle for an audience with the man who may soon become president.

Mr Zardari has also worked to rebuild his image. The wardrobe is now replete with well-cut suits, the salt-and-pepper moustache is neatly trimmed, and the slick, jet black hair is tightly combed back. In person, his manner is alternately charming and confident. He is plainly a person who spent much of his time in exile and jail reading. Party members have noticed a more reflective man, equipped with a broader vocabulary and an arsenal of quotations – ranging from Shakespeare to Jesse Jackson.

Yet his broad, teeth-baring smile is still occasionally broken by flashes of anger when he begins to rail against his critics. "He has been through a lot," said an aide. "He will forgive people, but his Baluch roots never allow him to forget. The old rivalries still play out in the back of his mind."

Now his main rivalry is with a man who twice jailed him. Mr Sharif, leader of the Pakistan Muslim League-N (PML-N), has constantly threatened to leave the coalition if the 60 judges ousted by Mr Musharraf are not immediately reinstated. He has suggested he may agree to his rival's candidacy is the judges are promptly reinstalled.

Yet Mr Musharraf's exit last week was a rare moment of unity for the two party leaders. Now he has gone, hostilities have resumed as Mr Zardari has again refused to reinstate the judges, including the former chief justice, Iftikhar Chaudhry.

Mr Zardari, who is from a feudal background in Sindh, was jailed twice, first in the early 1990s when his wife's first term in office was brought to a halt, and then again in 1997 when he second term abruptly ended.

During her second administration Mr Zardari earned the nickname Mr 10 Per Cent for allegedly demanding a commission on government contracts. He was also accused of being involved in the killing of Ms Bhutto's brother, Murtaza. When he was freed in 2004, Mr Zardari went to be with his family in the Gulf.

Prosecutors in other countries have also investigated Mr Zardari. While the fate of such inquiries is unclear, Newsweek reported last week that investigators in Switzerland were still looking into allegations that he received kickbacks.

Mr Zardari was able to return to Pakistan because of an arrangement signed by Mr Musharraf that granted him amnesty. However, Ms Bhutto had always intended that when she returned to launch her party's election campaign, her husband would remain in the background. Fate, it seems, did not agree.