Because of that, another possible successor is Wali ur-Rehman, who has helped control access to Mehsud and acted as a messenger between the Taliban chief and his deputy commanders along the Afghanistan-Pakistan border.
"This could lead to a crisis in the Taliban because there's no obvious successor," Rahimullah Yusufzai, an ABC News consultant and the Peshawar editor of the English daily newspaper The News.
U.S. and Pakistani officials blame Mehsud for some of the worst terrorist attacks in Pakistan, including the assassination of former Prime Minister Benazir Bhutto in Decrmbrt 2007.
In the last few months the United States has singled out Mehsud in its campaign, led by the CIA, to target senior Taliban and al Qaeda leaders using unmanned aerial drones. Initially, the drones generally targeted only al Qaeda commanders and some Taliban leaders who were more responsible for attacking U.S. soldiers in Afghanistan than was Mehsud.
But the United States put a $5 million bounty on his head. And of the last 10 drone strikes in Pakistan's tribal areas, nine targeted Mehsud or his network in the South Waziristan tribal agency. Wednesday's attack was at least the 29th this year, according to an ABC News tally.
His death is one of the most significant terrorists to be killed by the United States in years. Obama's head of counterterrorism, John Brennan, said the President has made the pursuit of terrorists a priority.
"Over the past six months, we have presented President Obama with a number of actions and initiatives against al Qaeda and other terrorist groups," Brennan told the CSIS yesterday. "Not only has he approved these operations, he has encouraged us to be even more aggressive, even more proactive, and even more innovative, to seek out new ways and new opportunities for taking down these terrorists before they can kill more innocent men, women and children."
Last month, a CIA drone strike nearly killed Mehsud when it hit a funeral he was attending. Instead, it killed 65 other people.
The Pakistani government has publicly criticized the U.S. attacks, but privately officials acknowledge that if the attacks do not kill civilians, they are helpful in defeating an insurgency embedded in some of the world's least hospitable terrain.
"I don't think it makes any difference who killed Baitullah Mehsud if he is indeed dead," Ispahani said. "It is a good day for Pakistan if he is dead because he was a murderer and he was a man who incited others to murder, and he did not care whether they were innocent civilians, or government servants, of people from military."
"If he is dead, though, it's unfortunate if it happened because of a drone attack, but as I said, with this particular case, at the end of the day, the end justifies the means," Ispahani said.
Pakistan has increased its attacks by fighter jets in the region but has steered clear of sending ground troops.
In an interview with al Jazeera in January 2008, Mehsud said he was fighting a "defensive" jihad against the West.
"Our main aim is to finish Britain, the United States and to crush the pride of the non-Muslims," he told al Jazeera at the time. "We pray to God to give us the ability to destroy the White House, New York and London. And we have trust in God. Very soon, we will be witnessing jihad's miracles." ABC's Huma Khan and Ammu Kannampilly and The Associated Press contributed to this report.