The problem with that scenario, though, is that Pakistani political parties are much more about strong, powerful individuals — like Musharraf, Bhutto or Sharif — than about the parties themselves. Secretary of State Condoleezza Rice telephoned Bhutto's second-in-command, Makhdoom Amin Fahim, to offer her sympathy and pledged to continue to support elections in Pakistan, administration officials said.

Bush's continued strong support for Musharraf could further erode his already declining popular support, even if the administration still sees his leadership as the best guarantor of Pakistan's nuclear arsenal.

"The danger is the centrist elements of Pakistan will be so demoralized," said Stephen P. Cohen, a senior fellow at the Brookings Institution. He criticized the administration for failing to nurture Pakistan's opposition for so long after Musharraf's coup in 1999. He expressed hope that the United States could still urge moderate parties to ally themselves with Musharraf, forming a governing coalition, assuming that the scheduled elections go ahead.

"It should wake up anybody who thinks that Pakistan is a stable country and that we can deal only with Musharraf," Cohen said of the assassination.