For this president, who has made national security a main theme of his re-election campaign, a lot depends on whether Americans accept that President Bush and his national security team were doing the best they could to protect us, given what they knew.
    
Analysis and opinion polls in the coming days will bring some indication of whether Mr. Bush has succeeded. Based on the evidence of the hearings of the September 11 commission, however, and based on Mr. Bush's own statements during the press availability with Egyptian President Hosni Mubarak in Crawford, my sense is that the American people will believe him.
    
Human beings do notactonthe unimaginable, and members of the U.S. government are - believe it or not - human, too. Threats that have no place in our worldview become, in effect, invisible. Only when catastrophe strikes does our view of the world change enough for the patterns to emerge from the mass of intelligence and information. Hindsight is 20/20, as they say.
    
In the absence of hard evidence that the September 11 plot was known in detail to the intelligence services, the question to which certain members of the September 11 commission keep returning is this:
    
Why didn't anyone in a position of authority imagine and take steps to prevent a terrorist plot to bring down the U.S. government and destroy our economy by using passenger aircraft as flying bombs against the World Trade Towers, the Pentagon and the White House?
    
And the answer they keep getting from Clinton and Bush administration officials alike is that no one had enough specific information or the vision to connect such "dots" as existed. Even the now famous - notorious, perhaps - Richard A. Clarke, whose book "Against All Enemies" heaped fuel on the controversy of who knew what and when, conceded in front of the September 11 commission that nothing he himself had proposed in the summer of 2001 would have stopped the attacks.
    
Not even the presidential daily briefing of Aug. 6, 2001, "Bin Laden Determined To Strike in U.S.," which was declassified over the weekend, contained enough specifics on which to act. "FBI information since [1998] indicates patterns of suspicious activity in this country consistent with preparations for hijackings or other types of attacks, including recent surveillance of federal buildings in New York," it says and mentions 70 bin-Laden-related FBI field investigations in the United States. Surely the president had a right to assume that FBI Director Louis Freeh would let him know when one of these investigations resulted in actionable intelligence.
    
One of the most important statements made by National Security Adviser Condoleezza Rice during her appearance before the September 11 commission was that "the terrorists were at war with us, but we were not at war with them." It can well be argued that the Clinton administration ought to have known - after the attacks on the U.S. embassies in Africa and the attack on the USS Cole in Yemen - that terrorists were waging war against us. But the Clinton administration saw isolated incidents, not a military strategy. And they treated the 1993 terrorist attack on the World Trade Center as a law enforcement matter.
    
As pointed out by Miss Rice during the hearings, the Clinton team bequeathed no effective plan against al Qaeda to the incoming Bush administration. Mr. Bush wanted to develop a plan that focused more broadly on undermining the radical Taliban regime in Afghanistan that gave bin Laden sanctuary and allowed him to train thousands of terrorists. Such a strategic plan was in the works in the summer of 2001.
    
At home, a major problem was that the very people we pay to imagine threats against the nation, intelligence agencies, were prevented from sharing what they knew. The FBI could not talk to the CIA or the Defense Intelligence Agency - as a matter of culture, tradition and long-standing U.S. legal practice. Only now, with the creation of the Homeland Security Department, the Terrorism Threat Information Center and the passage of the Patriot Act has that become possible.
    
In the end, the answer to all the September 11 commission's many probing questions about why the U.S. government missed the threat on September 11 may be that "no one could imagine it." After September 11, the world changed and so did our view of the dangers that face this country.