Back then, there were blacklists. Now, we've got no-fly lists. Then, we had the Doomsday Clock. Now, we've got the looming Code Red terror alert.

Schoolchildren trained a generation ago to duck for cover under their desks (as if that was protection from a nuclear bomb!). Now, they are parents who fine-tune their families' terror evacuation plans (and wonder: Can we really escape?).

We live once again in an era defined by fear, just as we did through nearly half the 20th century, during the Cold War.

Though it's been only three years since the Sept. 11 attacks launched the United States onto a war footing, it's clear, from all indications, that the war on terror is likely to go on and on. Condoleezza Rice, the national security adviser, compared the war on terror to the Cold War recently and noted the latter conflict took 40 years to win.

In three short years, we've already become accustomed to fear.

In profound ways, fear is redefining our lives, as well as the paradigm of our politics. Unlike the presidential election of 2000, this time we're voting with fear as a backdrop. Fear factors into our daily plans. We're reflexively responding to it, expecting the worst, as when that pepper spray episode on K Street last week seemed like a terror incident and sent the stock market tumbling. From fear.

Fear is real, even justified. But it is also a problem, some scholars say, for one of the greatest lessons of the Cold War is that we should be afraid, very afraid, of the things fear can make a society do. Just say the word: McCarthyism.

During the Cold War, we feared the "fellow travelers" in our midst. Now, we fear "enemy combatants." And the Constitution has again become a battleground over the rights of all citizens in order to protect us from a few.

But the fear of this age is very different.

"I think things are worse now, because it's the fear of the unknown," says Jerrold M. Post, professor of psychiatry and political psychology at George Washington University. He is former director of the CIA's Center for the Analysis of Personality and Political Behavior.

Our enemy today is very different from the communists of the old Soviet Union, he says.

"We knew them, and we knew we could count on their sensibility that they didn't want to be destroyed any more than we did."

But now, the enemy is a shadowy global network of Islamic militants whose hatred knows no national boundaries, who don't abide by the rules of war, who could be anywhere -- even right here -- ready to strike again. And unlike the Cold War days, when mutually assured destruction (known, yes, as MAD) kept both us and the Soviets from going over the nuclear edge, our enemies these days want nothing more than to die, taking mass casualties with them.

And so we wait. It's a matter of when, not if. We focus our fear everywhere, which means nowhere, since we don't know what we're looking for. So Metro plans evacuation drills. So the World Bank and IMF still soldier on under Code Orange, as targets. The days of duct tape may be behind us. But we need only reflect today on life and the tragic loss of it to realize that fear has unpacked its bags and moved into our homes.

It's kept us vigilant. But it's also become the political weapon of choice. We saw that during the Cold War, too. It was Sen. Arthur Vandenberg who created an enduring adage when he advised President Harry Truman to "scare the hell out of the country" to get his agenda through Congress. Some have come to believe that terror alerts and target lists have been used to stoke perhaps more fear than is necessary.

"Fear is essentially a political emotion, and a politically manipulated emotion at that," says Michael Ignatieff, director of the Carr Center at the John F. Kennedy School of Government at Harvard University.

"So we have to be wary, as citizens, of any political leader who says 'Be afraid. Be very afraid. And vote for me and you'll be safe.' "

In the Cold War, the infamous "daisy ad" did this, with Lyndon Johnson suggesting a Barry Goldwater victory in 1964 would lead to a nuclear holocaust. Critics this week have slammed Vice President Cheney for doing it, when he warned that a vote for Sen. John Kerry could mean the United States will get hit by terrorists again.

"Politicians fall in love with a threat, because it makes their lives much simpler, so George W. Bush believes that his electoral fortunes will rise and fall over how well he can portray himself as a leader in the fight against terror," says David S. Meyer, professor of sociology and political science at the University of California at Irvine.

"The war on terror is the trump card that obviates all debate, and Kerry is doing the same thing," Meyer says, referring to Kerry's use of his military record.

One thing Meyer sees as a difference between the fear of the war on terror and that of the Cold War is that fear in the 1950s and 1960s became an organizing principle for a whole domestic agenda not directly related to security.

To stay strong in the test of wills with the Soviets, we had to look strong at home. We had to bulk up in education, especially the sciences. We had to soar into space. We had to get rid of those moral blots on our house, such as rampant racial discrimination.

The United States was "taking propaganda beatings in Europe," says Meyer, because of the continuing inequalities in a system that touted itself as free.

That, he says, was the upside of fear -- it helped propel an agenda for social change. (Meyer himself benefited, attending college on a national defense student loan intended to help the country compete with the Soviets.)

"Same deal with the war on terror," he says. "The war on terror gives people legitimate reason to build our public health infrastructure, to improve the care in emergency rooms across the country."

But fear, he cautioned, also can be used to justify what politicians might want to do anyway. The war on Iraq could fall into that category, since there were many in government whose desire to take out Saddam Hussein predated Sept. 11, 2001.

The impulse to focus on a single enemy, a nation, is straight out of the Cold War -- and wrong, says Stephen Flynn, a senior fellow at the Council on Foreign Relations and a military official in both the George H.W. Bush and Clinton administrations. The enemy is not a state. It's an ideology and a methodology. The United States hasn't figured out how to fight it, he says.

"The United States is living on borrowed time," he writes in a fear-inspiring opening line to his article in the journal Foreign Affairs.

We are back where we started. Something bad is definitely going to happen.

"What a scary mode of fatalism we are in," writes Victor Davis Hanson, the classicist and military historian at the Hoover Institution.

So what are we going to do about it? What's the big-stick deterrent against terror? What's the threat of massive post-facto misery we could rain down on someone, somewhere?

Hanson's got an idea. We'll call it the war-on-terror version of MAD. Or the TFD strategy -- Targeted For Destruction.

Before another attack happens, the United States would issue a long list of military bases, power plants, communications and assorted infrastructure facilities and then destroy them in any country found to have aided or sheltered the terrorists, says Hanson, writing in the July issue of National Review. His strategy ignores the fact that terrorists don't necessarily need states to operate.

Hanson calls this "the awful nature of real war" and says the world should "shudder at the very thought of it . . . and stop looking at 'war against terror' as some sort of parlor game."

There is fear among us, for sure, like a nasty rash you just want to scratch till it bleeds.

We must be wary, says Flynn, quoting a general he knows, that "the real damage is what we will do to ourselves. . . . When we have a sense of generalized vulnerability, and when politicians play on our fears, that's when the real harm can be done."

Now: Police patrol a Metro car in August after a security alert.

Then: A 1946 atomic bomb test at Bikini Atoll in the Pacific.