After its initial shock and spontaneous sympathy the world is coming to terms with the serious threat posed by the assassination of Benazir Bhutto. Pakistan's status as one of the world's most unstable and combustible countries has been fully confirmed by Thursday's atrocity. If, as seems plausible, it was the work of al-Qaeda jihadists, perhaps working with elements of the intelligence services, it could bring closer the possibility of them increasing their influence or even trying to take power in this nuclear-armed and strategic state. Ms Bhutto and her party were one of the main bulwarks against that prospect. Her murder is a grave setback for those who resist such movements, as well as a terrible tragedy for her distinguished family.
Her return from exile to fight the elections gave rise to hopes that she might forge a partnership with Pakistan's president, Gen Pervez Musharraf. It would wean Pakistan off military rule towards a more democratic politics based on the rule of law. That strategy now lies in ruins and it is hard to see how political order can be retrieved in the immediate future. No final decision has yet been made about whether the elections will be postponed. But they should and must be held. Without them the military will be unable to govern alone with any legitimacy. Ms Bhutto held out the promise that the vibrant movement behind this year's protests against Gen Musharraf's arbitrary rule could be harnessed politically. Her death should reinforce the efforts to strengthen Pakistan's weak party system.
For most of its independent history Pakistan has been ruled by the military or parties associated with them, usually ones with Islamic roots. This reflects the country's origins in the British partition of the sub-continent along religious lines, subsequent wars with India and the 1971 conflict over East Pakistan that led to the foundation of Bangladesh. During the 1980s Gen Muhammad Zia-ul-Haq's regime received massive military aid from the United States and Saudi Arabia to prosecute the mujahideen war against Soviet-occupied Afghanistan - a model Pakistan's rulers also applied in Kashmir. Ms Bhutto's two periods as prime minister in the 1990s interrupted that pattern, which resumed when Gen Musharraf seized power in 1999.
Afghanistan loomed large again after 9/11, giving him vital leverage in the "war on terror" proclaimed by President Bush against al-Qaeda and its leader Osama bin Laden who still survives in the ungoverned border region between the two states. Military links with Islamist movements have a long history. The Bush administration has had to take account of it as they sought Pakistani aid against al-Qaeda and the Taliban. The US-inspired effort to forge an alliance between Ms Bhutto and Gen Musharraf was highly risky for both of them, but made good political sense. It is an immense challenge to find an alternative way to govern Pakistan's 166 million people now that she is gone.