YOU don't have to win the Nobel Prize for Economics to become President of the United States. You don't have to be relentlessly decent, impossibly wise and thoroughly noble to occupy the Oval Office. You don't, as a general rule, have to care too much about how you came by your election, or about the improbable number of weapons of mass destruction you are allowed as Commander-in-Chief. Such notions are fiction.

But some people wish, even now, that the fiction was fact. Just before George W Bush came to power, to take a case in point, American bumper stickers and badges carried the motto 'Vote Bartlet.' Ironic but defiant, they were suggesting a generally unbelievable character from a slightly believable TV show was a better bet than the Republican candidate. Martin Sheen's President in the The West Wing may have represented an impossible dream, but the contrast with Bush -- a man who, of course, was eventually rejected by just over 50% of US voters -- was compelling.

It continues to resonate. Sheen's record as a 'liberal' Hollywood activist, his reliable appearances at a host of demonstrations and his 70 arrests, attracted little real attention before he took command of the fictional West Wing. To nobody's surprise, the actor has spoken vehemently against a war with Iraq; now, to the surprise of some, all hell has broken loose. Which 'President' does America support?

To be more precise, Sheen's stand and the responses to it have raised a number of questions pertinent to his country's democracy as it prepares for war in democracy's name. First, as a host of right-wing talk-radio hosts have been asking: where do super-rich performers get off using their celebrity, glamour and access to the media to influence the political process? Who, in other words, elected them?

In response, one half of a divided country wants to know why any citizen, famous or not, should be denied the right to free speech. What they are referring to is the pressure that has reportedly been put on Sheen's network, NBC, to sack him from The West Wing. The actor claims he has been called on to 'explain his views' to his bosses who are, he adds, 'very uncomfortable.' He says he has been deluged with hate mail.

Other performers argue that they have been obliged to exploit their fame because America's media have imposed a regime of self-censorship.

So is this the new McCarthyism? Once upon a time, when Senator Joe was rampaging through Washington, the line of inquiry was simple : 'Are you now, or have you ever been, a member of the Communist Party?' But today the mechanisms for moral cause and effect are more obscure.

Nobody (at least on paper) wants war. The motives for supporting conflict are as diverse, in some quarters, as the motives for opposing it. With the cold war at an end and one superpower now dominating the planet -- and with sincere support for Saddam Hussein thin on the ground -- Sheen has become the lightning rod for a new storm in Western society: are you now, or have you ever been, anti-American?

Back in the 1950s, conservatives had a simple formulation. My country, they would say, right or wrong. Yet Sheen claims to be a proud patriot. He and others like him refuse to give up the right to be heard. They are, in any case, producers of what the world knows as American culture. The 50 musicians who recently put their names to a full-page anti-war ad in The New York Times are not obviously 'un-' or 'anti-' American. Lou Reed and REM? As American as the Manhattan skyline.

Passions are running high, in any case, in part because of the reverence many Americans have for the office of President. It is a reverence few Europeans understand, but to some of Sheen's fellow citizens it clarifies the entire issue. In times of war you trust and follow the man in the Oval Office. Dissent, and you insult the office. Insult the office and you insult America. If you happen to be a dissenting Hollywood phoney, your guilt is merely compounded.

It is interesting, nevertheless, to see celebrity become the grounds for attack in what is supposed to be a celebrity-obsessed age. The stars have no more actual rights than anyone else, but everyone knows they enjoy many more privileges than we mortals. So why, some Americans ask, allow a person whose only talent is for mouthing scripts (other than the President) to undermine the government and, potentially, give aid and comfort to terrorists?

If the inferences are sound, then it is a good question. September 11 left many Americans in no mood to mess around with their security. They see Hollywood liberal posturing as so much self-indulgence from people safely tucked away in mansions, and patronising to boot. And who hasn't been irritated by some celebrity posing as an expert demanding their time, their money or their attention?

But then where does this sort of backlash lead? Do we boycott Red Nose Day because Lenny Henry is not, in fact, a specialist in famine relief? More seriously, do we go on tolerating all the rhetoric about the defence of democracy when democratic standards are being steadily eroded -- the attempt to shut up Sheen being a prime example?

His offence, in any case, was simply to participate in a TV advertisement and a 'virtual' march on Washington. Launching the former, Sheen said: 'Our message to Washington will be clear -- don't invade Iraq. We can contain Saddam Hussein without killing innocent people, diverting us from the war on terrorism and putting us all at risk.'

The idea behind the 'march,' meanwhile, was to bombard Washington politicians with e-mails, faxes and telephone calls in protest against the war. Organised by the Win Without War group that has brought together 32 charities, pressure groups, churches and other organisations, it persuaded at least 200,000 individuals to make more than 400,000 phone calls and send 100,000 faxes to senators and the White House. The reaction, if not the desired result, was instant.

First came Citizens Against Celebrity Pundits, an online petition and campaign website. Founded -- so it is claimed -- in a moment of exasperation by Lori Bardsley, a North Carolina housewife, it accuses the stars of using their celebrity to undermine their country's defence.

'Anti-war activism is hip, but September 11 was real,' Bardsley has said. 'On September 11 our children were threatened. We expect President Bush to take whatever measures necessary to keep us safe.' She also claims the celebrities do not speak for most Americans. By last Thursday, days after its launch, her petition boasted 30,531 signatures as evidence.

'We the undersigned American Citizens stand against Wealthy Hollywood Celebrities abusing their status to speak for us,' the petition says. 'We do not believe that they have a clear understanding of how we live, what we fear, and what we support.'

One signatory is a little less measured. He writes: 'I will not go to the movies. I will not support their television shows, I will not buy their music. My family and I shall boycott supporting anyone in Hollywood until they decide their job is for entertainment value only.' Meanwhile, GIJargon.com, a website claiming to represent the US military, police and firefighters, has denounced protesting celebrities as 'Taliban' and also called for a boycott of 'anti-American entertainers.'

Hollywood's Screen Actors Guild has been here before. During the era of studio blacklists in the 1950s more than 300 actors and writers were forced out of the industry under suspicion of Communism. Having received a slew of hostile mail directed at Sheen and others, therefore, the SAG last week issued a statement on its website. 'Some have recently suggested that well-known individuals who express 'unacceptable' views should be punished by losing their right to work,' the union said. 'Even a hint of the blacklist must never again be tolerated in this nation.'

Professor John McCumber of the University of California, Los Angeles, scents McCarthyism -- but he makes one distinction. In 1950s Hollywood people, afraid of being depicted as 'reds', spoke out far less than anti-war activists do now because they were fighting for their careers, and because they had less ready access to the mass media. In contrast, modern celebrities are seen simply as dupes. 'It's hard to portray Martin Sheen as affiliated with Arab terrorists,' says McCumber, 'so he's portrayed as a dupe.'

Steve Rendall of Fairness & Accuracy in Reporting (FAIR), a New York-based left-of-centre watchdog group, points out that celebrities have the same constitutional rights as anyone else. He also recalls actress Janeane Garofalo's explanation of why she speaks out -- because she believes the media ignore anti-war activists who could speak more eloquently. 'She can get the microphone. She can get the camera,' he says.

For his part, Paul Bond of the Hollywood Reporter says he always receives many e-mails after a TV appearance from people who say they hate celebrities dabbling in politics. He tends to agree. 'If the celebrities go to rallies that seem anti-American, there will be a backlash. Viewers see TV coverage of the peace rallies, in which placards liken Bush to Hitler and where American flags are burned. [Viewers] see Saddam as an enemy of America who will be killing American soldiers.'

In the early 1950s, the investigators of the House UnAmerican Activities Committee were not only demanding answers to their simple question on Communism, but coercing witnesses to 'name names,' to inform. In the midst of a struggle against a vast and vastly dangerous enemy, as its government believed, America went to war with itself.

The consequences can still be seen today in a country almost equally divided in its attitudes, and riven over the methods and purpose of war. Those same divisions destroyed the US war effort in Vietnam. And just how do you have a democracy in which the only speech is approved speech?

Let Sheen have the last word, while he still can. Interviewed recently by CNN, he too invoked patriotic duty: 'I can't even begin to tell you how much I love my country. I love it enough to risk its wrath by pointing out the things that will destroy it, harm it very deeply. And that's costly patriotism.'

Additional reporting by Ros Davidson