Of course, the United States is not vulnerable to the violent, total closing-down of the system that followed Mussolini's march on Rome or Hitler's roundup of political prisoners. Our democratic habits are too resilient, and our military and judiciary too independent, for any kind of scenario like that.

Rather, as other critics are noting, our experiment in democracy could be closed down by a process of erosion.

It is a mistake to think that early in a fascist shift you see the profile of barbed wire against the sky. In the early days, things look normal on the surface; peasants were celebrating harvest festivals in Calabria in 1922; people were shopping and going to the movies in Berlin in 1931. Early on, as WH Auden put it, the horror is always elsewhere - while someone is being tortured, children are skating, ships are sailing: "dogs go on with their doggy life ... How everything turns away/ Quite leisurely from the disaster."

As Americans turn away quite leisurely, keeping tuned to internet shopping and American Idol, the foundations of democracy are being fatally corroded. Something has changed profoundly that weakens us unprecedentedly: our democratic traditions, independent judiciary and free press do their work today in a context in which we are "at war" in a "long war" - a war without end, on a battlefield described as the globe, in a context that gives the president - without US citizens realising it yet - the power over US citizens of freedom or long solitary incarceration, on his say-so alone.

That means a hollowness has been expanding under the foundation of all these still- free-looking institutions - and this foundation can give way under certain kinds of pressure. To prevent such an outcome, we have to think about the "what ifs".

What if, in a year and a half, there is another attack - say, God forbid, a dirty bomb? The executive can declare a state of emergency. History shows that any leader, of any party, will be tempted to maintain emergency powers after the crisis has passed. With the gutting of traditional checks and balances, we are no less endangered by a President Hillary than by a President Giuliani - because any executive will be tempted to enforce his or her will through edict rather than the arduous, uncertain process of democratic negotiation and compromise.

What if the publisher of a major US newspaper were charged with treason or espionage, as a rightwing effort seemed to threaten Keller with last year? What if he or she got 10 years in jail? What would the newspapers look like the next day? Judging from history, they would not cease publishing; but they would suddenly be very polite.

Right now, only a handful of patriots are trying to hold back the tide of tyranny for the rest of us - staff at the Center for Constitutional Rights, who faced death threats for representing the detainees yet persisted all the way to the Supreme Court; activists at the American Civil Liberties Union; and prominent conservatives trying to roll back the corrosive new laws, under the banner of a new group called the American Freedom Agenda. This small, disparate collection of people needs everybody's help, including that of Europeans and others internationally who are willing to put pressure on the administration because they can see what a US unrestrained by real democracy at home can mean for the rest of the world.

I believe that the Bush administration's systematic effort to expand presidential power is among the most interesting and defining themes of this era in Washington -- one that unites and explains many different policy controversies which are too often discussed in isolation from one another or without reference to the larger pattern.