Americans are destined to worry about terrorism approximately forever.

Five years after that blue-sky Tuesday turned dark with death and rubble, longer now than the U.S. fought in each world war of the last century, the essential characteristics of the terrorists haven't changed, nor the nature of the confrontation. No treaty is possible, no truce to be had, no Mission Accomplished banner contemplated as far ahead as anyone can see.

The terrorists are endlessly sneaky, clever in some ways, almost comically bumbling in others, and seemingly replenished as fast as they can be killed or captured. Hopelessly outmatched in any head-to-head confrontation, but impossible to stomp out. And always lethal because it only takes a few with a brain wave, or one with a strapped-on bomb, to cause mass death.

Five years after the Sept. 11, 2001, attacks, the government says it lives every day like it's Sept. 12, 2001. That's an exaggeration — the country is not on highest alert — but there are, at least, both visible and invisible sentries at work always.

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Combat air patrols comb the skies with new post-9/11 powers to shoot down civilian aircraft. They've logged more than 42,000 flights. Ships at sea prowl for incoming dangers with new authority to intercept suspicious vessels. Unseen eyes monitor movements and communications in ways that have never been.

The government's squishy mantra: Safer but not safe.

Expect never to hear this: We're safe. Relax.

There are indications Americans are taking a fork in the road when it comes to the impact of the threat on their lives. At first, everyone walked on eggshells.

Now, AP polling loosely finds two levels of worry based on where people live. More than half of the people in New York and Washington are concerned about their cities being attacked, polling suggests. Less than one third of Americans overall have this concern about where they live.

But half the people surveyed both in targeted cities and nationally say the attacks changed the way they live to this day. And most worried that the war in Iraq has made a terrorist attack on the U.S. more likely.

Absent another attack, a low-grade disquiet persists, one that spiked up when the British foiled the alleged plot to blow up U.S.-bound airliners in the sky. Americans boarding airplanes scan seat-mates and make snap judgments of character.

Anything suspicious trips a hair-trigger sensitivity. Nearly one in five Americans polled for AP reported suspicious activities or people in recent months.

"Now, if somebody moves toward the cockpit or somebody leans down to light their shoe, I think three people are going to jump them," Thomas Kean, the former Republican New Jersey governor who was co-chairman of the 9/11 commission, told AP. "And I think that makes me feel much more secure than anything government's done."

More secure, but not secure.

"There are an awful lot of people out there who want to do us harm," Kean went on. "And it's very hard to believe that somebody is not going to get through."

Five years later, the portrait is hardly one of a traumatized nation. Rather, a nervous one where life goes on, people travel and gather in crowds. The ban on carryon liquids and gels prompted by the recent plot was quickly adjusted so people would not be put out too much: Solid lipstick is OK, mascara is not.

Al Qaeda targeted national and economic symbols; despite its catastrophic success that one day, the New York and Washington economies are thriving, the Pentagon is whole again and the U.S., a fat target with penetrable borders and openly discussed security loopholes, has so far escaped another assault.

Yet the definition of success is as elusive as the meaning of safer.

"They say we're winning because there hasn't been a detonation of explosives in the U.S.," said Mike Scheuer, who led the CIA group that hunted Osama bin Laden until it closed last year — mission not accomplished.

"Well, Al Qaeda is fighting us in two wars overseas, in Afghanistan and Iraq. ... bin Laden remains free and his organization continues to function. Our budget deficit is spiraling. The amount of money we're spending on homeland security and defense is astronomical.

"And when you look at it from bin Laden's perspective, of how he's defined this war, he's defined it as bleeding America to bankruptcy. I would say that America has been under attack every day since 9/11."

Bin Laden drifts in and out of U.S. discourse according to political expedience.

Republicans avoid mentioning him when it serves them not to remind people he's remained on the loose while Americans went into Iraq. Democrats do the same when it serves them not to remind people they still prefer Republicans on matters of terrorism, if not on much else.

Bin Laden has been out of the debate more than in, but President Bush brought him back in a big way after the traditional Labor Day kickoff of the fall campaign. Bush discussed Al Qaeda's ambitions, ideology and strategy at unusual length. "Hear the words of bin Laden," he kept saying.

Bush quoted Al Qaeda lieutenants and papers, too, on the forever nature of the struggle.

"There will be continuing enmity until everyone believes in Allah," Bush quoted. And he related this warning from the organization: "The whole world is an open field for us."