A week after the death of Osama bin Laden, al-Qaeda still has not publicly anointed a successor, and the most likely heir apparent could prove to be a divisive figure within the terrorist network.

U.S. counterterrorism officials and analysts said they expected that Ayman al-Zawahiri, an Egyptian surgeon and bin Laden’s longtime deputy, would take over as al-Qaeda’s emir, or paramount leader. But they added that his ascendance was not guaranteed, pointing to a statement released Friday by al-Qaeda’s “general command” that acknowledged bin Laden’s demise but gave no hint of who was in charge.

“Zawahiri is obviously the presumed successor, but there are strong indications that he is not popular within certain circles of the group,” a senior U.S. intelligence official told reporters Saturday in a briefing at the Pentagon. “It is, of course, anathema to al-Qaeda to hold free and fair elections. If free and fair elections [were conducted], Zawahiri would most likely have a fight on his hands.”

Another U.S. official, who also spoke on the condition of anonymity to discuss intelligence assessments, noted that while many al-Qaeda sub-commanders have been killed in recent years, there are alternatives to Zawahiri.

Among them are two veteran Libyan jihadis, Atiyah Abd al-Rahman and Abu Yahya al-Libi. “Atiyah or Abu Yahya are rumored to be more personable than Zawahiri and have certainly earned their operational chops,” the official said.

Al-Qaeda’s central organization is formally governed by a shura, or leadership council. Most of its members had sworn an oath to serve under bin Laden. It remains to be seen whether Zawahiri or his rivals will be able to command the same loyalty.

U.S. officials are hoping that the trail that led them to bin Laden’s hideout in Abbottabad, Pakistan, will also take them to Zawahiri, who has been al-Qaeda’s operational commander for years. Over the past week, the CIA has been trying to exploit an intelligence windfall of materials collected from bin Laden’s compound, including possible information on the whereabouts of other al-Qaeda figures. U.S. officials briefed on the effort have hinted that Zawahiri is among those being pursued aggressively, and the chairman of the House intelligence committee said last week that he believed “we’re hot on the trail.”

Zawahiri’s stature as a theoretician and intellectual is unquestioned in Islamist radical circles. He lacks bin Laden’s personal magnetism, however, and has alienated many allies with his uncompromising leadership style and prickly personality.

“He is the master ideologue of the global jihad,” said Fawaz Gerges, a professor of Middle Eastern studies at the London School of Economics who has studied Zawahiri and the history of al-Qaeda. “There is no one else who has his weight or intellect. He is a giant among the remaining figures in al-Qaeda. But there is no doubt Ayman al-Zawahiri has been a divisive figure.”

After the Sept. 11, 2001, attacks, Zawahiri gradually became the most visible face of al-Qaeda, issuing dozens of video and audio propaganda statements while bin Laden receded into the shadows, surfacing only occasionally to remind the world that he remained at large.

In his last video, released April 14, Zawahiri spoke for nearly 70 minutes but did not mention bin Laden. Such omissions would have been highly unusual a few years ago but have become more common in Zawahiri’s statements, underscoring the perception that he was effectively in charge.

The video shows the dour, bespectacled Zawahiri dressed in white and flanked by his usual prop, a military-style rifle. His visage is marked by a pronounced callus in the middle of his forehead, the result of decades of extremely pious behavior in prostrating himself to the ground in prayer.

Over the years, the Egyptian surgeon has gained notoriety for his no-holds-barred rhetoric. In November 2008, he called President Obama a “house Negro” who was a stooge of Israel. He also doesn’t spare other jihadist leaders from his hectoring. “He always thinks he is right, even if he is alone,” Montasser el-Zayat, an Islamist lawyer in Cairo who has known Zawahiri for 30 years, said in a 2006 interview.

Zawahiri’s books and speeches are circulated widely by al-Qaeda sympathizers, who discuss and annotate them as a source of guidance and inspiration, said Rita Katz, executive director of the SITE Intelligence Group, which monitors Internet traffic from jihadist Web sites.

Since bin Laden’s death, there has been relatively little discussion in Islamist chat rooms about Zawahiri’s fitness to replace bin Laden, Katz said.

“The jihadists do not obsess over who is the number one or number two leader of a particular group,” Katz said. “In fact, it is not clear if bin Laden needs to be replaced with an official number one leader, as this type of structure is not necessarily needed for a decentralized organization such as al-Qaeda.”

Radical roots

Zawahiri was born into a prominent, well-educated Egyptian family. His relatives included a founding member of the Arab League and a chief imam of the al-Azhar mosque in Cairo, the historic center of Islamic learning in the Arab world.

As a teenager, however, Zawahiri quickly embraced the radical politics that came to define his life. After Egypt’s disastrous loss to Israel in the 1967 Six-Day War, he and other university student conspirators began plotting for the day when they could replace Egypt’s secular regime with a theocracy.

After President Anwar Sadat was assassinated in 1981, Zawahiri and hundreds of other Islamists were rounded up. According to his account and those of other prisoners, he was tortured, which further hardened his resolve to topple the government.

He went into exile after his release from prison, moving to Saudi Arabia, Pakistan, Sudan and eventually Afghanistan. He was leader of the Egyptian Islamic Jihad, a group seeking to overthrow Egyptian President Hosni Mubarak. And he bonded with bin Laden, a wealthy Saudi six years his junior who shared his commitment to jihad.

Although the two formed a close partnership, he waited until July 2001 to merge his group — which by then was bereft of money and lacking in followers — with al-Qaeda. Two months later, al-Qaeda launched its attacks on the World Trade Center and the Pentagon.

In its 500-page report on the plot, the Sept. 11 Commission mentioned Zawahiri only a handful of times, focusing on the role played by bin Laden and other operatives. Analysts, however, said that Zawahiri’s influence on the group should not be minimized.

“He has always run al-Qaeda. He was there at every strategic juncture,” said Bruce Hoffman, a Georgetown University professor and counterterrorism adviser to the U.S. government. He said it was Zawahiri and other Egyptian jihadists who possessed the skills and experience to transform an Afghan guerrilla movement into an international terrorist organization.

“He may not be as charismatic as bin Laden, but he is an extremely devout and faithful Muslim who is also very learned and capable, and that’s what counts,” Hoffman said. “We’re used to thinking in John F. Kennedy terms, but they’re thinking about leaders who have religious gravitas as well as leadership capabilities, which Zawahiri does have.”

In his home country, however, Zawahiri, 59, is increasingly seen as an irrelevant relic of a prior age.

For decades, he insisted that violence and terrorism were the only way to bring about political change in Arab countries. The mostly peaceful revolutions in Egypt and Tunisia have proved him wrong and drowned out his message, analysts said.

Amr al-Shobaki, a professor at the al-Ahram Center for Political and Strategic Studies in Cairo, said al-Qaeda enjoyed a brief period of popular Arab support after the Sept. 11 attacks. But that dwindled rapidly after it resumed terrorist plots in predominantly Muslim countries.

“Al-Qaeda, through its violent operations in the Arab states and all over the world, has lost all sympathy,” Shobaki said said. “At one time, al-Qaeda and also al-Zawahiri were representing the voice of the disappointed Arab people. But now, with the public realization that the people can bring about change, there is no sympathy for him at all.”

Staff writer Greg Miller in Washington, special correspondent Haitham Tabei in Cairo and staff researcher Julie Tate in Washington contributed to this report.