First published: Friday, December 28, 2007 A politically unstable Pakistan poses a danger to world peace. That has been so since Pakistan assembled a nuclear arsenal that could someday fall into the hands of Islamic extremists as part of a coup. On Thursday, when former Prime Minister Benazir Bhutto was assassinated at an election rally in Rawalpindi, the danger posed by a volatile Pakistan became ever more so. Already many of Ms. Bhutto's followers are accusing the government of President Pervez Musharraf of having a hand in the assassination, and tension is sure to mount in the streets. That can only increase the chances that extremists, most of them loyal to Osama bin Laden, who is believed to be hiding somewhere in Pakistan's ungoverned western provinces, will exploit the unrest in an attempt to seize power. This is a challenge for the Bush administration, which must bear some responsibility for placing Ms. Bhutto's life at risk. It was widely reported that the White House had brokered an agreement with the Musharraf government last October to allow Ms. Bhutto to return from eight years of exile and mount a political comeback by running in the parliamentary elections scheduled for early next month. Her return was meant to be a show of democracy at work in Pakistan, and to answer the critics who had been accusing the White House of tolerating the dictatorial ways of Mr. Musharraf simply because he was an ally in the war on terror. But it backfired almost from the start. Ms. Bhutto narrowly escaped assassination during her homecoming parade in Karachi, when a suicide attacker killed 140 people. And it wasn't long before Mr. Musharraf imposed emergency rule (since lifted), cracking down on the press and political demonstrations and purging Pakistan's Supreme Court of judges who were believed to have been ready to rule against Mr. Musharraf's hold on the presidency. Shortly after Ms. Bhutto returned to Pakistan, she accused officials in the Musharraf government of plotting with Muslim extremists to assassinate her. Later, she hired her own security guards to accompany her to rallies and accused the Musharraf government of failing to adequately protect her safety. Her charges are sure to be revived by her supporters in the days to come. Thus, the Bush administration faces a dilemma. It can't disregard the legitimate concerns of Ms. Bhutto's supporters who believe the government either orchestrated her assassination, or turned a blind eye to those who plotted it. But at the same time, Mr. Musharraf now has more bargaining power with the United States, which has been pressuring him to restore the court system and release political prisoners, while also doing more to hunt down al-Qaida and its supporters. The White House must find a way to keep up that pressure, while also working to prevent the Musharraf government from collapsing amid the turmoil around it. THE ISSUEakistan's former prime minister, Benazir Bhutto, is assassinated. THE STAKES:If political upheaval follows, extremists could seize power.