Conventional wisdom would point the finger at Islamic extremists in Pakistan as the ones who pulled off the successful assassination of former prime minister Benazir Bhutto. They made no secret of the fact that killing Bhutto was their number one priority.

They despised her relative secularism and the fact that she was a woman doing man's work. But most of all, they needed to kill her in order to bring unrest to Pakistan, thus setting the stage for what they hope could turn into a bloody civil war and the victory of extremists.

In this scenario, al-Qaeda and those who sympathize with them both in and out of government could be responsible for her death. The intelligence service, ISI, has many Islamist sympathizers in its ranks and getting through the security that surrounded Bhutto could have been facilitated by the professionals in Pakistani intelligence. As details of the attack are revealed, that aspect of the puzzle may come together.

Who else might have carried out such an attack? The Pakistani people are apparently blaming President Musharraf, thinking he offed her in order to get rid of a rival for power. Or, their reasoning goes, he had Bhutto killed in order to re-establish some kind of one man rule.

The problem with blaming Musharraf is that the last thing the Pakistani president wants at this point is violence in the streets. Dawn is reporting that tear gas is already being used against protestors in Peshwar and the possibility of millions of Pakistanis rioting in the major cities is Musharraf's main nightmare at the moment. This is not to say, as I mention above, that elements of the government weren't in on the plot. But Musharraf would have to have a death wish to kill Bhutto.

Is it possible that this was a lone nut? Possible but not very likely. Security surrounding Bhutto was several layers deep and it would seem extremely unlikely that someone could wander through the security net and blow himself up. This is why the finger keeps coming back to a detailed plot with perhaps complicity among  Bhutto's bodyguards. The reason for that speculation is that early reports indicate that shots were fired inside the vehicle immediately before the suicide bomber detonated himself. It could be that the bomber was able to push his way into the car following Bhutto who witnesses say was shot as she was getting into the car.

The next few days will tell the tale for Pakistan and its efforts to bring democracy to the country. Elections, scheduled for a little more than two weeks from today, will feature a new leader of Bhutto's Pakistani People's Party. Can he or she fill Bhutto's shoes?

If not, Pakistan is in for some very dangerous times.

Update: Thomas Lifson adds:

Is there a connection between the killing of Bhutto and Musharraff's campaign in the Swat Valley?  Quite possibly.

From December the 8th ABC News (Australia - not related to American ABC News), the Pakistani Army is claiming the Swat Valley is clear of Islamist militants.  Musharraff's forces have killed 290 rebels and arrested another 143, but pro-Taliban cleric Maulana Fazlullah is still on the run with about 200 to 400 "hardcore fighters, including some foreigners." 

It's not unreasonable to assume that remnants of  Fazlullah's forces are behind the attack on Bhutto given that they were kicked out of the Swat Valley almost three weeks ago and are desperate to continue their campaign of de-stabilization.  Also, Maj Gen Janjua of the Pakistan Army says it will take about four months to completely restore order in the Swat Valley.  In the meantime, pro-Taliban forces could very well have dispersed and then regrouped to conduct the attack.

Update from Marc Sheppard: