THE OBAMA administration’s descriptions of what happened Sept. 11 in the Libyan city of Benghazi have evolved in a way that some — including congressional Republicans — find suspicious. Initially, Secretary of State Hillary Rodham Clinton described an “attack” in which “heavily armed militants” assaulted a U.S. compound, leading to the death of Ambassador J. Christopher Stevens and three other Americans. Four days later, U.N. Ambassador Susan Rice said that “extremist elements” had joined a demonstration outside the U.S. Consulate against an anti-Muslim video.

By the end of last week, White House spokesman Jay Carney was calling the incident a “terrorist attack” but adding that it was likely “the result of opportunism” and not planned. But then Wednesday, Ms. Clinton suggested that al-Qaeda’s North African branch, operating from a safe haven in Mali, could have had a hand in the assault. Al-Qaeda and other terrorists, she said, “are working with other violent extremists to undermine the democratic transitions underway in North Africa, as we tragically saw in Benghazi.”

Critics see in this a deliberate attempt by the administration to portray the Benghazi violence as a spontaneous response to the video, as opposed to a terrorist attack that was timed for Sept. 11 and possibly planned by al-Qaeda. Sen. John McCain (R-Ariz.) and three other Republicans have demanded in a letter that Ms. Rice explain how she “could characterize an attack on a U.S. consulate so inaccurately,” while a group of congressmen accused the administration of adopting “a pre-9/11 mind-set — treating an act of war solely as a criminal matter.”

In fact, political calculations appear to have infected the rhetoric of all sides. The White House was slow to place the modifier “terrorist” in front of the word “attack,” at a time when President Obama claims credit on the campaign trail for the “decimation” of al-Qaeda. He continued to focus on the offending video — which also provoked demonstrations outside U.S. embassies in Cairo and around the Muslim world — long after it became clear that the Benghazi attack was the work of well-organized combatants who, among other things, accurately aimed mortar fire at an unmarked U.S. compound located half a mile from the consulate.

Still, it is not yet clear that Libyan government officials are correct in their own, self-interested claims that the attack was pre-planned for Sept. 11 by al-Qaeda leaders outside of Libya. Many residents of Benghazi blame members of a local militia, Ansar al-Sharia, which in turn has conceded that some of its members may have joined in a spontaneous attack on U.S. installations. Such extremist groups were known to be encamped around Benghazi and heavily armed; it’s not implausible that they would have acted opportunistically.

The sensible and responsible response to this foggy situation is to refrain from further loose talk and allow the investigations by the FBI and the State Department to proceed, with the collaboration of intelligence agencies and the Libyan government and regular briefings for Congress. The probe should cover not only what occurred on Sept. 11 and who carried it out, but why U.S. facilities in such a dangerous city did not have better protection. Perhaps sensible and responsible is a lot to ask this close to an election — but given the tragic loss of U.S. life in this case, it ought to be possible.