Readers of Hello! in Asia were this month treated to a cover shot of Bena- zir Bhutto reading You Can Do It! The motivational tome by Paul Hanna had its intended effect. After posing for the celebrity magazine in her Abu Dhabi home, one of several gilded mansions she maintains around the world, the 54-year-old politician left behind her children and husband and embarked on the third act of her political career, one that could give her a chance to make amends for two dismal previous stints as Pakistan's prime minister.

Her return has not gone to script. After months of negotiations with General Pervez Musharraf over a "transition to democracy", her euphemism for a pact that would have seen her provide a civilian front to his military rule, Ms Bhutto arrived to find herself tainted by association. Although a homecoming parade in Karachi on October 18 at-tracted a large crowd, the turnout, before it was dispersed by blasts that left 140 dead, was a fraction of the 3m she claimed. Subsequent rallies have been lame affairs, with cameramen and police outnumbering her well-heeled supporters.

Even when Ms Bhutto was placed under house arrest on Monday, many suspected she was only going through the motions in condemning Gen Musharraf's decision, two weeks ago, to impose de facto martial law. She had, after all, much to gain from his assault on the judiciary: a compliant Supreme Court would be unlikely to throw out the decree providing an amnesty to politicians facing corruption charges filed by 1999. Promulgated by Gen Musharraf as a condition of their deal, it benefited her but excluded key cases against her rival, Nawaz Sharif, another former prime minister.

But this week, as the government's clampdown on the media and arrest of thousands of lawyers, human rights activists and other moderate Pakistanis threatened to take a further toll on her popularity, Ms Bhutto was forced into a radical change of tactics. On Tuesday, under pressure from her Pakistan People's party, she burnt her bridges with the general, promising she would never serve as prime minister as long as he was president. Lamenting the "total trust deficit" between them, she declared that anyone who associated with Gen Musharraf would be "contaminated".

Reached by telephone as she was detained by paramilitaries, she told the Financial Times the deal was off. "I have decided there can be no further negotiations," she said. "Back channel negotiations between the PPP and Musharraf ended after [the] emergency. There's no chance of those being revived." If she maintains this stance - and her release from house arrest on Thursday night does not seem to have softened it - the US-brokered agreement between the army chief and the leader of the country's largest political party would be dead.

By withdrawing a last democratic lifeline from Gen Musharraf, Ms Bhutto deprives him of his best chance of securing broader legitimacy for his rule. Although he has announced that elections will be held by January 9, he has refused to lift the state of emergency. There is little prospect that the main political parties, their candidates jailed, deported or in hiding, will participate. Whether the army, sensitive to the damage being done to its image and to the risk that the flow of dollars will dry up, will support an extended period of virtual martial law is not clear.

"I didn't choose this life; it chose me," Ms Bhutto often says, revealing the extent to which political leadership is seen as a birthright in south Asia. Ms Bhutto is the custodian of the most valuable brand name in the region after India's Gandhi dynasty and she has traded on the legend of her father, Zulfikar Ali Bhutto, demagogic founder of the PPP. The first democratically elected prime minister after the civil war that led to the creation of Bangladesh in 1971, Bhutto was deposed by General Muhammad Zia ul-Haq in 1977 and hanged two years later.

The Bhutto name lost lustre during her abbreviated stints as prime minister, 1988-90 and 1993- 96. These ended in a welter of corruption cases against her and her bon vivant husband, Asif Zardari. A Swiss prosecutor is mulling whether to move ahead with a money-laundering case, while probes are under way in Spain into her role in the United Nation's oil-for-food programme in Iraq. Ms Bhutto, who this year hired an affiliate of US lobbying firm Burson-Marsteller to burnish her image, maintains the cases are "politically motivated".

There is deep cynicism about her motives. A poll by the International Republican Institute in Washington found that 47 per cent of Pakistanis believed she was acting to "improve her personal situation", with only 27 per cent saying she was motivated by a desire to bring democracy back to Pakistan. Harvard and Oxford educated, Ms Bhutto has been more successful in appealing to the US State department's desire for a democratic facade in Pakistan than in reviving the love she once engendered in her people.

Few sovereignty-conscious Pakistanis approve of the way she has wooed the Pentagon, the source of roughly 60 per cent of the almost $11bn (£5.5bn) that the US has given Pakistan since 2001. Washington was "enticed" by her assurance that she would let US troops hunt al-Qaeda and other extremists in Pakistan and also allow International Atomic Energy Agency inspectors to question A.Q. Khan, who sold nuclear secrets to Iran, Libya and North Korea, Tariq Azeem, Pakistan's state minister for information, said recently.

While her return from the political graveyard reflects the poverty of choice in Pakistan's political system, it has also been an extraordinary feat of willpower. Her challenge now will be to overtake politicians such as Imran Khan, the former Pakistan cricket captain who was arrested this week under anti-terrorism laws, and Mr Sharif, deported on his attempted return to Pakistan, who have benefited from their more confrontational poses. The IRI's poll suggested Mr Sharif's popularity began outstripping Ms Bhutto's in September.

On Thursday, Ms Bhutto swallowed her pride and telephoned Mr Sharif, suggesting they re-form a common front to oust Mr Musharraf. Her attempts to present herself as the unifier of Pakistan's democratic opposition may be laughable to those who have borne the brunt of the military crackdown, but it is a matter of urgency for the PPP. If the promised January elections are free and fair - a big if - Ms Bhutto will have to move fast if she is not to be caught up in the backlash against those who flirted with the military.