The assassination of opposition leader Benazir Bhutto deals a stunning blow to liberal political forces trying to combat rising Islamic extremism in Pakistan.
Gathering unrest by her supporters also risks tipping the volatile country into chaos, and puts more pressure on President Pervez Musharraf as he struggles to keep order and stay in power.
It quashes hopes of Western governments that the charismatic, two-time former prime minister could team up with Musharraf and galvanize Pakistan's fight against Taliban and al-Qaida militants after Jan. 8 elections, which are now in doubt.
"This assassination is the most serious setback for democracy in Pakistan," said Rasul Baksh Rais, a political scientist at Lahore's University of Management Sciences. "It shows extremists are powerful enough to disrupt the democratic process. Musharraf's major concern now will be to maintain law and order and make sure this does not turn into a major movement against him."
Bhutto died Thursday when an attacker shot her and then blew himself up as she left a political rally in Rawalpindi, a city near the capital where Pakistan's army has its headquarters. It was the second suicide attack against her since her tumultuous homecoming from an eight-year exile in October.
Government plunged into turmoil
The other key opposition leader, Nawaz Sharif — whose government was ousted in the 1999 coup that brought Musharraf to power — quickly announced he was boycotting the parliamentary elections, which are meant to usher Pakistan toward civilian government after years of military dominance.
Talat Masood, a retired general and now a political analyst, expected Bhutto's party to follow suit — a move that would rob the vote of legitimacy.
Bhutto had accused elements in the ruling party of backing militants to kill her — claims that could gain more traction now despite government denials.
At the very least, the government will appear to be losing its grip over Pakistan.
"Conditions in the country have reached a point where it is too dangerous for political parties to operate," Masood said.
He anticipated that Musharraf, who recently suspended the constitution for six weeks, could take drastic steps.
"It is possible they could declare an emergency again," he said.
But Musharraf, who was himself targeted twice in Rawalpindi by al-Qaida bombers in December 2003, gave no immediate sign of an authoritarian backlash to Bhutto's assassination. He declared three days of national mourning and vowed to fight the terrorists behind her killing.
Only a few months ago, he held direct talks with Bhutto and paved the way for her return from exile.
A country on the edge
Anthony Cordesman at the Center for Strategic and International Studies in Washington, warned that any suspicion that Musharraf had a role in Bhutto's killing or knew about the plot and failed to prevent it could pitch Pakistan "to the edge of civil conflict."
"Much will depend on whether some Islamist extremist movement announces that it committed the attack, but even then a substantial number of Pakistanis will still see the Musharraf government as being at least indirectly involved," he said.
Sharif, a longtime rival of Bhutto, sounded a defiant note after the assassination of Bhutto, and her supporters rampaged across Pakistani cities.
"We will take the revenge on the rulers," a tearful Sharif said after he rushed to the Rawalpindi hospital where Bhutto was pronounced dead.
Western allies, particularly the U.S. and Britain had hoped Bhutto and Musharraf could unite against a growing militant threat and galvanize the campaign against terrorism amid signs that al-Qaida's leadership has reconstituted itself inside Pakistan, posing a risk to global security.
"In a society becoming increasingly intolerant, she was being viewed by the international community as a person who could make a difference as a moderate politician, who, if she came to power, could turn the tide of religious extremism in this country," said Zaffar Abbas, an editor for the respected Dawn newspaper.
Cordesman stressed the domestic turmoil spawned by Bhutto's slaying was unlikely to endanger the safety of Pakistan's nuclear arsenal. The government has rejected suggestions that Islamic militants might assault or infiltrate secret facilities where the weapons are stored.
"They are not stored where public riots or demonstrations can affect them, and there is no reason the military should become unstable or their security should be compromised," Cordesman said.