The New York Times reports: Libyan authorities have singled out Ahmed Abu Khattala, a leader of the Benghazi-based Islamist group Ansar al-Sharia, as a commander in the attack that killed the American ambassador to Libya, J. Christopher Stevens, last month, Libyans involved in the investigation said on Wednesday.

Witnesses at the scene of the attack on the American Mission in Benghazi have said they saw Mr. Abu Khattala leading the assault, and his personal involvement is the latest link between the attack and his brigade, Ansar al-Sharia, a puritanical militant group that wants to advance Islamic law in Libya.

The identity and motivation of the assailants has become an intense flash point in the American presidential campaign. Republicans have sought to tie the attack to Al Qaeda to counter President Obama’s claim that by killing Osama bin Laden and other leaders his administration had crippled the group; Mr. Abu Khattala and Ansar al-Sharia share Al Qaeda’s puritanism and militancy, but operate independently and focus only on Libya rather than on a global jihad against the West.

On Monday, the New York Times reported: To those on the ground, the circumstances of the attack are hardly a mystery. Most of the attackers made no effort to hide their faces or identities, and during the assault some acknowledged to a Libyan journalist working for The New York Times that they belonged to the group. And their attack drew a crowd, some of whom cheered them on, some of whom just gawked, and some of whom later looted the compound.

The fighters said at the time that they were moved to act because of the video, which had first gained attention across the region after a protest in Egypt that day. The assailants approvingly recalled a 2006 assault by local Islamists that had destroyed an Italian diplomatic mission in Benghazi over a perceived insult to the prophet. In June the group staged a similar attack against the Tunisian Consulate over a different film, according to the Congressional testimony of the American security chief at the time, Eric A. Nordstrom.

At a news conference the day after the ambassador and three other Americans were killed, a spokesman for Ansar al-Shariah praised the attack as the proper response to such an insult to Islam. “We are saluting our people for this zeal in protecting their religion, to grant victory to the prophet,” the spokesman said. “The response has to be firm.” Other Benghazi militia leaders who know the group say its leaders and ideology are all homegrown. Those leaders, including Ahmed Abu Khattala and Mohammed Ali Zahawi, fought alongside other commanders against Col. Muammar el-Qaddafi. Their group provides social services and guards a hospital. And they openly proselytize for their brand of puritanical Islam and political vision.

They profess no interest in global fights against the West or distant battles aimed at removing American troops from the Arabian Peninsula.

Nevertheless, the group’s motivation became a source of disagreement. At last week’s Congressional hearing, Mr. Nordstrom tried to contradict lawmakers who insisted that the group was at least “loosely affiliated with Al Qaeda.”

Representative Dan Burton, Republican of Indiana, cut him off. “Don’t split words,” he said. “It is a terrorist organization.”

Some analysts argue that the White House, meanwhile, sought to play down any potential characterization of the assault as a Qaeda attack, because that would undercut its claims to have crushed Al Qaeda.

Libyan guards at the Benghazi compound and other witnesses told journalists working for The New York Times as early as Sept. 12 that the streets outside the mission were quiet in the moments before the attack had begun, without any prior protests.

Other Benghazi militia leaders who know Ansar al-Shariah say it was capable of carrying out the attack by itself with only a few hours’ planning, and as recently as June one of its leaders, Mr. Zahawi, declared that it could destroy the American Mission.

The Wall Street Journal adds: In Libya, the Americans have only a threadbare presence and thin security ties. The FBI team in Tripoli is interacting primarily with the nascent Libyan intelligence agency headed by former U.S. citizen Salem al-Hasi, a veteran Libyan political dissident who for decades lived in the Atlanta area and taught Arabic to U.S. soldiers, according to several Libyan officials.

Mr. Hasi has no direct control over the existing security bodies in Benghazi, whose commanders have forces to make arrests there. In Tripoli, meanwhile, civilian leaders are struggling to form a new government, leaving the nation without strong ministers of the interior or defense.

Other aspects of the American investigation, including the treatment of witnesses, are also generating criticism among Libyans.

Some witnesses from Benghazi have traveled at their own expense to meet with FBI investigators and share information with them. Three of these witnesses say the Americans have offered them no protection in exchange for their cooperation, prompting two of them to say they are trying to dissuade other Libyans from talking to the bureau. The FBI team has spent only a handful of hours on the ground in Benghazi, saying the city is too insecure.

For those who share Rep. Burton’s perspective, it matters little who conducted the attack since differentiating between different groups, their affiliations and their ideologies amounts, supposedly, to splitting hairs. But as the Century Foundation’s Michael Hanna pointed out to the New York Times, those who are linking the attack to al Qaeda are making “promiscuous use” of the term. “It can mean anything or nothing at all.”