Editor's note: Peter Bergen is CNN's national security analyst and a fellow at the New America Foundation in Washington and at New York University's Center on Law and Security. His most recent book is "The Osama bin Laden I Know: An Oral History of al Qaeda's Leader."
Peter Bergen says there may be several reasons for Osama bin Laden's silence.
(CNN) -- If the audio message purportedly from al Qaeda's deputy leader is authentic, we have finally heard from a representative of the terror organization about the American election.
It was wholly expected that there would be such a tape, though the content, with its references to Malcolm X might be considered somewhat surprising --although in recent tapes al Qaeda's leaders have occasionally referenced critics of American society and foreign policy such as Noam Chomsky and Malcolm X.
On the tape, the deputy leader, Ayman al-Zawahiri, seeks to make President-elect Barack Obama seem like an apostate for his support of Israel and the war in Afghanistan: "You were born to a Muslim father, but you chose to stand in the ranks of the enemies of the Muslims, and pray the prayer of the Jews, although you claim to be Christian, in order to climb the rungs of leadership in America."
Still, the tape does not resolve the mystery of why we didn't hear from one person who was supposed to weigh in on the American presidential election: Osama bin Laden.
Four years ago, the al Qaeda leader appeared in a well-lit videotape addressing himself directly to the American people five days before they voted in the contest between Sen. John Kerry and President Bush.
Bin Laden said then that whoever won the election was immaterial as far as al Qaeda was concerned and that instead, Americans needed to change their country's foreign policies in the Muslim world, or face the consequences.
U.S. intelligence officials tracking al Qaeda had been expecting a similar message from the al Qaeda leader in the run-up to this presidential election. Yet, bin Laden did not appear.
There could be several reasons for this. First, the bin Laden tape might still be in the pipeline and will surface in coming weeks after having wended its long way via a chain of couriers from his hide-out on the Afghan-Pakistan border to be uploaded to a jihadist Web site or delivered to an Arab TV station.
Second, bin Laden may have concluded that, given the widespread expectation that he would deliver an election-eve tape, discretion is the better part of valor and for security purposes, now is not the time to make an appearance on the world stage.
Third, militant targets in the tribal regions have been the subject of more than 20 American missile attacks this year -- nine in October alone, according to a count by CNN's Pakistan bureau -- and that may have spooked the al Qaeda leadership, which has not been the subject of such intense missile strikes previously.
Those attacks are designed not only to disrupt al Qaeda's operations, but also to increase the radio or phone communications between militants -- signals intelligence known as 'SIGINT' -- that can be traced by American spy agencies, according to U.S. intelligence and administration officials who track al Qaeda.
The open question -- if the tape is authentic -- is why al-Zawahiri has been able to get his message out, while we have heard nothing from bin Laden.
The opinions expressed in this commentary are solely those of Peter Bergen.