After the night of the bloodbath, Bhutto's days of reckoning

Waving flags and a wall of raw noise. Handfuls of petals and grinning faces. Cheers and excitement.

As she set off from Karachi airport on Thursday atop a customised truck, Benazir Bhutto, 54, twice prime minister of Pakistan and twice deposed by the military, would have felt entitled to dream that she could attain the prize a third time. Returning from eight years in exile, she smiled and waved back at her supporters, and wiped away tears. At times, her face may have given away her nerves and anxiety, but she could barely have asked for better welcome.

She said as much herself. Having negotiated the enthusiastic if clearly inadequate ring of security volunteers surrounding her convoy, I clambered on to the truck and joined Ms Bhutto on the top deck. She said she felt "overwhelmed by the love and support of the people". Asked if she was really prepared to throw herself back into the hurly-burly of front-line politics after her time away and eight years of a more sedate, less intense existence, she insisted: "Very much so ... I have been getting practice by meeting with the exile communities of Denmark and the US."

At the time, with the raw, unfiltered emotion of south Asian politics on show all around, the comment sounded a little naive. Less than 10 hours later, with her triumphant return to Pakistan having been transformed into bloody chaos by an assassination attempt that killed more than 130 people and left hundreds more injured, it appeared ludicrous. Yet in its own way, that throwaway remark might reveal a crucial flaw in Ms Bhutto's determined plan to win an historic third term as Pakistan's leader – a plan brokered by the US and Britain, and dependent upon a power-sharing arrangement with President Pervez Musharraf.

Having lived for so long in the glass bubble of exile, is Ms Bhutto now too out of touch with the realities of her country to achieve her ambition? Can she allay the doubts that have always surrounded her: that while she comes across in the West as an Oxford-educated liberal, in office she behaved more like a feudal princess than a modern politician? And do her people still love her?

That, of course, was partly the point of the plodding, snail-paced procession through the streets of Karachi to the grave of Mohammad Ali Jinnah. There, the plan went, having metaphorically wrapped herself in the fabric of Pakistan's founder, she would address a huge crowd of supporters who had travelled to Karachi from across the country. This was to be the day to bring Karachi to a standstill: even if the crowds were not as large as they were in April 1986, when she returned from a previous period of exile to challenge General Muhammad Zia-ul-Haq – the military dictator who had led a coup against her father and then ordered his execution – it would still make a point that everyone could see.

Destiny, believed the daughter of Zulfikar Ali Bhutto, was on her side. And at first things had appeared to be going so well. The crowds were large and enthusiastic. Having bussed in supporters from all parts of Pakistan, officials from Ms Bhutto's Pakistan People's Party had ensured hundreds of thousands were waiting for her. Some might have been there simply because they were told to go, others simply because they were curious. Some had been paid £4 a day – a lot of money to a poor person in Pakistan – to attend. It did not matter. What was essential was that the television cameras that evening would reveal large, noisy crowds and a waving Ms Bhutto making her way through them.

Shortly after midnight that plan came off the rails. Moments after the convoy passed beneath the Karsaz Bridge over Sharea Faisal, the long road that runs from central Karachi to the airport and beyond, a young man was seeing running diagonally through the crowd towards the convoy.

Though for some reason the street lights were not working at this point – an issue that Ms Bhutto has demanded be investigated – party workers told police the man was illuminated by the arc lights they were using to monitor the crowd. There was an initial small explosion, apparently as he threw a grenade. Then, according to police, he detonated the explosive vest he was wearing, carrying a massive charge. Video footage of the explosion showed a blast of noise followed by orange light and flames.

The results were terrible. Scores of people were mown down in a welter of blood, severed limbs and charred flesh. At the city's beleaguered Jinnah Medical College Hospital, ceiling fans failed to dissipate the muggy smell of disinfectant and blood as the casualty department quickly overflowed. A group of three young doctors, standing together in a brief moment of respite from their labours, said they had never had to deal with so many shrapnel injuries. They were angry and emotional, their eyes red with exhaustion. "We have given everything to save these people. We have given our spirit. But sometimes it has been hopeless," said Dr Shaikh Hamid.

Within hours, Ms Bhutto – lifted shaken but uninjured from her truck – was seeking to turn events to her favour. She was rushed to her in-laws' home in the elite Clifton district of Karachi, where she sat down with Paris Match magazine and told them that supporters of the former dictator, General Zia, were behind the attack.

By later on Friday afternoon at a press conference for scores of foreign journalists, she had honed her message. The assassination attempt against her had been carried out precisely because she stood for democracy and moderation. The attempt on her life was "an attack on democracy and an attack on the very unity and integrity of Pakistan". She also claimed that intelligence, passed to her party by officials from a "brotherly" Muslim country, had warned that at least four separate suicide cells were planning to attack her. This information had been passed on to the government of General Musharraf, she added.

What Ms Bhutto did not answer was why, given what she and her aides knew, they had continued with the planned procession. Why had she accepted that so many people should be put at risk? Analysts believe the attack will boost her support, and in a country where political cynicism plumbs the depths, many will assume she was aware of that.

Whatever the answer, Ms Bhutto's thoughts will now return to her campaign. Her senior aides had realised that while the PPP might have a broad base of support, her presence on the campaign trail was essential if the party was to make the sort of impression it wished for in the parliamentary elections planned for January. The rapturous response she received fuelled their hopes.

"I guess prospects in Pakistani politics are indeed enhanced by the kind of welcome she's received," said Nasim Zehra, a political analyst and newspaper columnist. "A lot of people who were critical of her participation in a US-brokered deal that wipes away her corruption charges were humbled by the outpouring of support on the streets of Karachi." As for the bombing, "the sympathy factor can kick in [after] something like this. It illustrates to people from all sections of society how real the threat of terrorism is in the Pakistani public space."

Quite how Ms Bhutto can spearhead the PPP campaign, given the security operation that will now have to surround her, is unclear. Party activists agree that despite the dangers, they must continue to organise rallies in the run-up to the election. And to a greater or lesser extent, Ms Bhutto must continue to campaign in public. There is talk in her camp that she might now make smaller, unannounced appearances at events.

"We have a strong tradition of festivities, demonstrations and long processions – it's part of the political culture of south Asia," said Nusrat Javed, host of the political discussion show Bolta Pakistan. "If there are to be credible elections, then the political parties cannot be stopped from leading these rallies, which are essential for them to be able to draw support."

Ms Bhutto's plan to begin her campaign in dramatic style, by speaking to the crowds at Jinnah's grave, has already been thwarted. The next stage was to have been an equally theatrical procession to her ancestral home near Larkana in rural Sindh. There she was to pay her respects at the grave of her father, further embellishing the sense of destiny she has sought to promote. But while she is still expected to go, the event will be much more muted, with security everywhere.

Friends of Ms Bhutto say her plans are in flux, but that there is a determination the show should go on. After a week that saw her receive, in every sense, a homecoming she could not have dreamt of, Ms Bhutto will have to decide how badly she wishes to fulfil her ambition. She will also have to consider the price both she and others may have to pay for her to do so. But if she believes she is fulfilling her destiny, no cost may seem too high.

Additional reporting by Omar Waraich in Islamabad