“Assassination”, Benjamin Disraeli declared after the death of Abraham Lincoln, “has never changed the course of human history.” This is a noble sentiment but one that will be sorely tested after the murder of Benazir Bhutto yesterday.

For the past few years, diplomats and other observers have referred privately to the prospect of the killing of Pervez Musharraf as the “nightmare scenario” for international order. In a subtle recognition of the way in which power had already evolved in Pakistan, even before a vote had been cast, the demise of Ms Bhutto had become the possibility the outside world most dreaded. Now that she has been the victim of a suicide attack not only Pakistan but also the United States, Britain, and the EU will have to renew their commitment in the fight against terrorism.

The murder of Ms Bhutto is as shocking, sadly, as it is unsurprising. There has already been wild speculation as to who might be to blame, with accusations levelled at President Musharraf either directly or indirectly for his failure to provide her with enough protection. In other circles, it has been suggested that renegade elements of the notoriously independent intelligence services could have been complicit in this atrocity. In the next few days, the debate as to who bears responsibility will be heated.

It must not be allowed to get out of hand or become destructive. The notion that the Pakistani President might be at the heart of this affair is far-fetched. He is undoubtedly a loser as a result of her murder. Ms Bhutto had so many enemies that even in the so-called garrison city of Rawalpindi it would not have been feasible to keep all hostile elements away from her. Security had been increased but it could not be absolute. There are many extremist factions in Pakistan that would want to be rid of her, because of her gender, or out of a sense that she was a comparatively secular figure, or because of her links to the American Administration, or because she would probably have been prepared to reach an understanding with President Musharraf had she won the elections.

None of this will stop the rumours and the conspiracy theories from circulating. It is, therefore, in the interests of the President as well as the rest of Pakistan that her death is the subject of an investigation that is unambiguously independent in character. This will not convince everyone of the facts but a searching inquiry, which reasonable people would accept is beyond political manipulation, can secure a degree of stability.

Death has magnified Ms Bhutto's undoubted virtues and will render her a martyr. She had charisma and courage on an extraordinary scale. There was absolutely no need for her to return from exile in London and Dubai when her life was plainly in danger. Victory at the polls would have meant that she inherited an unenviable series of challenges. Her previous periods as Prime Minister had not been without controversy or disputes and to have taken the office again in the circumstances that were certain to occur would have been yet more perilous. Her willingness to make that personal sacrifice was profoundly honourable. The fear must be that her loss will discourage others entering politics.

The overwhelming question now is what happens next. It was manifest from the moment that her death was announced that the original election timetable was imperilled. It would be hard to avoid postponing a ballot in an established democracy in the light of a deed such as this, but the election would be an invitation to anarchy in the Pakistani context. Ms Bhutto's party is entitled to some time to select a new leader and determine how it should proceed from here while security arrangements for all sides will have to be re-examined as a matter of urgency. The grim reality is that those who plotted Ms Bhutto's death are likely to be emboldened by their success and not cowed by the reaction.

The full restoration of democracy sooner rather than later has to be Ms Bhutto's final legacy. Pakistan has endured a miserable history over the past six decades, swinging between uneasy civilian rule that has often had the stench of corruption alongside it and military dictatorship that has arguably been more clean but lacked legitimacy. Until this miserable pattern is ended, the country will never achieve its immense potential.

The coming time thus demands that President Musharraf does not weaken in his resolve and that the United States and Britain — the two countries that have long enjoyed the most constructive dialogue with him — reinforce such a strategy. He can no longer rely on Ms Bhutto, or those who will take the reins of her party soon, to forge an alliance with him. He has to reach out to sections of the democratic opposition that he has ignored so far.

Chaos and violence would be no tribute to Pakistan's lost leader. Ms Bhutto was a fine patriot and a pragmatist. She was also a woman who sought to recognise and balance the enduring nature of her own society with the requirement for Pakistan to embrace many aspects of the contemporary world. In the best meaning of the phrase she will be remembered as a moderniser. There can be no modern Pakistan without democracy. After a comparatively short delay, elections should occur.

The military should emerge from the barracks only to ensure sufficient order for the Pakistani people to return to the ballot box. Ms Bhutto's murder was designed to destroy Pakistan's right to choose. To honour her memory Pakistan must show that democracy will always triumph over murderous extremism.