The camera zooms in on the handsome young spin-doctor, looking ruggedly photogenic in his denim jacket and open-necked shirt. It's the day before the presidential election and he's taking a call that threatens to torpedo his candidate. He's calm and cool, but he wears a look of steely determination.

"I could," he's saying into the phone, "send you a fax with names, addresses, phone numbers of who you had an affair with. It wouldn't make it true. Believe me that it's been looked at by every major national news organisation - everything - and it's completely bullshit. If you went on the radio and said that Bill Clinton is the father of an illegitimate black child, you would be laughed at."

There's a slight pause, then he speaks again, now with a vague but perceptible edge of threat in his voice. "I guarantee you that if you do this, you will never work in democratic politics again. You will be embarrassed before the national press corps. Nobody will believe you and people will think you're scum."

It's a scene from a movie, of course, and a superb piece of plotting. On the brink of victory, a sensational allegation threatens everything. Up on the screen, as a cinematic moment, it is powerfully tense and suspenseful. But it is too wild for real life, too luridly dramatic.

Except that the movie is real. The scene is from The War Room, D.A. Pennebaker and Chris Hegedus's brilliant fly-on-the-wall documentary about the 1992 Clinton campaign. The call is from the director of Ross Perot's campaign in Illinois. The handsome spindoctor is George Stephanopoulos. And the man he is defending really is about to become the President of the United States.

Fast forward to early 1996. Clinton is preparing to run for re-election. An anonymous novel, Primary Colors, becomes a national and international bestseller, partly because its central character, Governor Jack Stanton, is a thinly disguised Bill Clinton. It is read, not as fiction, but as the inside story of the 1992 campaign.

At a key point in the novel, the narrator, an idealistic young man working for Stanton on the 1992 presidential primaries has to deal with a black man who arrives at his office. The man is an old friend of Stanton's and he has a painful problem. "My daughter Loretta. . .", he says hesitantly, "She. . . with child. And she say Governor Jack Stanton's the daddy." The bizarre allegation has moved from a documentary that seems fictional to a work of fiction that is read as fact.

Fast forward again to January 1998. The anonymous author of Primary Colors has been outed as the journalist Joe Klein, now with the New Yorker. With allegations of sexual scandal and cover-up again swirling around Clinton, Klein writes a high-minded editorial for the magazine. It complains of "media firestorms, unreliable in their import". It points to a "febrile atmosphere", to a "witchhunt mentality".

Meanwhile, the movie version of Joe Klein's novel, with John Travolta made to look and act as much like Clinton as possible, is scheduled for its American release in March.

There is, indeed, a febrile atmosphere surrounding Clinton since the allegations of sex, lies and audiotape broke last week. Rumours - like for instance the belief that Bill Clinton admitted under oath that he did have an affair with Gennifer Flowers - have been reported as fact. Allegations - like the one that Clinton and Monica Lewinsky were caught in flagrante by a secret service officer - have been made in blazing headlines, then quietly withdrawn, leaving their stain on public consciousness. Tangible pieces of evidence - like the dress purportedly stained with Clinton's semen - have changed their status in the course of any given day from fact to fiction to something in between.

Here is a political story in which one of the principle protagonists, the literary agent Lucianne Goldberg, who got Linda Tripp to make the controversial tapes of her conversations with Monica Lewinsky - is also a professional ghost-writer. Her past credits include a political sex scandal novel, Washington Wives, published under the name of Maureen Dean, whose husband John was a key figure in the Watergate affair.

There never was a golden age when the workings of power were transparent and the full truth was always known. But neither was there a time when the public was bombarded with so many images.

The scandal is the clearest expression yet of this new reality and what it means for politics. But it didn't come from nowhere. It expresses a shift in American culture that has been increasingly obvious through the 1990s. One of its first manifestations was Oliver Stone's film on the assassination of John F. Kennedy, JFK. Its plot was a mixture of fact and conjecture, taking the known truths of history and providing a conspiracy theory to explain them. But much more importantly, its visual style often made it impossible for the viewer to tell documentary footage, re-creations of real events and pure inventions from each other.

Or consider Larry Beinhart's 1993 novel, American Hero, on which the current movie, Wag the Dog, is based. In it a president beleaguered by a sex scandal invents a war to distract attention. In a preface, Beinhart noted drily: "There are those who feel that fact and fiction are significantly less distinguishable than they used to be." He also remarked that presidents "have come to be judged by the standards by which we judge fictional characters who appear on our TV screens."

And he then went to compound the confusion himself. Unlike the movie, the novel deals with a real president, George Bush, and a real war - the second Gulf War in which the US and its allies defeated Iraq. It proposes, semi-seriously, a theory - that the Gulf War was deliberately engineered to boost Bush's popularity.

Beinhart mused in the novel on the effect of a media-saturated society on the presidency itself: "The only guy who could handle being on-camera every public minute and come out of it looking good was the guy who spent his life on-camera, Ronald Reagan. If the experiment with Bill Clinton is no more satisfactory than those with Nixon, Ford, Carter and Bush, then perhaps Reagan will turn out to be the harbinger of things to come, and the practice of having someone `act' as president will be institutionalised."

But perhaps it already has been. For if the media and cultural industries are partly responsible for the confusion of fact and fiction, then the other part of the blame lies with the political process in general and with Bill Clinton in particular.

During his 1996 re-election campaign, for instance, Clinton held a major event in a town called Hill Valley. The place where his stage was set up looked like a real, if unusually pretty, town square with a gas station, and an old oak tree and a grand court house. It was a vision of an ideal America. Except that Hill Valley was on the backlot of Universal Studios in Hollywood. It was the set for the three Back to the Future movies. Clinton's slogans for the election were all about building a bridge to the future. So his handlers thought it would be a good idea to use as a backdrop for his ideas the mythical town from which Michael J. Fox went back and forth in a time machine.

To make things even weirder, the featured speaker at the event, apart of course from Clinton himself, was the movie actor Michael Douglas. In the film, The American President, he had just played a Democratic president whose archenemy is, like Clinton's challenger Bob Dole, an older senator from Kansas.

As reported by Roger Simon in his fascinating new book on the 1996 election, Show Time, Michael Douglas's speech was that of a fan admiring a movie star: "While I was working on The American President, I would think about the real president. I would think about his stamina and his incredible knowledge of so many subjects. And I just want to say. . ." Here he turned to Clinton. ". . . Mr President, I'm a fan. I enjoy your work."

This event wasn't a weird, accidental clash of cultures. It was consciously and deliberately arranged, down to the last detail, by Bill Clinton and his campaign staff. They wanted the great American public, watching clips on the television news, to associate Clinton's bridge to the future with Michael J. Fox's time machine. They wanted the audience to think of the fictional hero of The American President as an adoring fan of the real president. They wanted the glittering allure of Hollywood to surround Clinton's own image.

And this event was exceptional only in being a more extreme expression of politics as usual in the television age. Reflecting on the 1996 campaign after it was all over, the White House spokesman Mike McCurry told Roger Simon: "This is the first campaign I know of where we really beat the other side by a country mile on stagecraft." A key presidential advisor, the television producer Harry Thomason, told Simon that "TV shows and movies and political events are all the same. They are all designed to move people."

When political events are designed to look like movies, and the movies are designed to hint at hidden political truths, is it any wonder that the public finds it hard to separate fact from fiction?