Mr Thomason flew into Washington nine days ago to coach Mr Clinton for a televised cameo performance that may go down as the most critical and dramatic episode of his entire presidency. Mr Clinton's brief, blunt and categorical denial on Monday that he had sexual relations with Monica Lewinsky abruptly turned the tide of a scandal that threatened to sweep away his family, his reputation and his political career. That 20-second burst of outraged indignation, timed to precision to meet the sound-bite exigencies of national network news, marked the beginning of a counter-offensive so successful that by the week's end his popularity had soared and his tenure at the White House looked as unassailable as, only seven days earlier, it had looked precarious.
In weekend rehearsals with Mr Thomason, whose professional speciality is made-for-TV movies, the President practised over and over again the hard, earnest, accusing glower, the punctuating jabs of the finger that will be remembered for ever by the millions who watched at home. He did not fail his instructor. When the lights came on, he trained his laser eyes on the cameras and, like John Wayne facing down the bad guys, delivered his script:
"But I want to say one thing to the American people. I want you to listen to me. I'm going to say this again. I did not have sexual relations with that woman, Miss Lewinsky. I never told anybody to lie. Not a single time. Never. These allegations are false."
The President's legal advisers, undeceived about their man's weakness for female flesh, had been opposed to him making a statement so categorical, so impossible to retract. But Mr Clinton made his political calculations and judged that desperate straits required desperate measures. Over the weekend some of the most judicious Washington veterans had been lining up before the TV cameras to predict his downfall; traumatised presidential staff members had been pondering what their next career moves would be; and - most alarming of all - internal White House polls had showed that he was sinking fast.
AFTER the woolly, non-denial denials with which he had initially responded to the Washington Post story that broke on Wednesday 21 January, he knew he had to gamble all on one bold throw of the dice. It was the highest of high-risk options because, by addressing himself so intimately to "the American people", he removed all the complex legal issues from the political equation and reduced the matter of his survival to a simple question of public trust.
From that moment on it mattered a great deal less whether Kenneth Starr, the Whitewater special prosecutor, would be able to prove in a court of law that the President had suborned perjury, urging Ms Lewinsky to lie about an affair. Now what mattered most was whether Mr Starr, in the course of his legal inquiries, would deliver evidence so irrefutable that the President's blanket denial of a sexual relationship with Ms Lewinsky would be exposed for the whole world to see as a bald-faced lie.
Even sex is no longer the issue now in the matter of Clinton vs Lewinsky. The polls have been taken, the media's samplings of public opinion have been exhaustive, and - evidence once more that a week is a long time in politics - the verdict is in. The American people, rejoicing as they are in a glut of economic prosperity, simply don't want to know what their winningly telegenic President gets up to behind closed doors.
Which means the issue is Mr Clinton's integrity, his commitment to truth, his possible abuse of presidential power. And answers could yet emerge sufficiently damaging to plunge him back into an even worse crisis than the one he weathered so adroitly last week.
What if, for example, a fine, upstanding, all-American Secret Service agent appears in court, or before the television cameras, and solemnly declares that he caught the President and Ms Lewinsky engaged in a sexual act?
What if Ms Lewinsky herself appears on the Oprah Winfrey Show and weepily confesses all, portraying herself convincingly as the impressionable doe cajoled by a caddish commander-in-chief, like a workhouse girl by a satanic 19th-century mill owner, into getting down on her knees and servicing his baser needs?
WHAT IF a taped conversation from a telephone answering machine surfaces, or a photograph, or DNA evidence - or something impossible to imagine right now - that conclusively demonstrates a sexual link?
In each case he would stand accused of lying brazenly to the American people and, as Democratic partisans were saying last week, "if he's lying, he's gone - simple as that".
His position as President would become unsustainable and, while the offence would not warrant impeachment, he would be faced with a choice between resignation and the indignity of limping through to the end of his presidency in the full knowledge that he would be viewed as a figure of ridicule for the rest of time.
Yet, as of this weekend, the odds are with the President. If anyone looks as if his career is on the line it is Mr Starr, who has spent four years and $30m of public money battling unavailingly to prove Mr Clinton's perfidy in matters ranging from the Whitewater financial scandal, to FBI Filegate, to Travelgate, to the dubious allegations that Vince Foster, the presidential aide who committed suicide, was murdered.
Quite apart from Mr Clinton's masterfulness as a political operator, Mr Starr and all the president's accusers have had to con-
tend with his formidable wife. Her performances on national morning television on Tuesday and Wednesday rammed home the advantage Mr Clinton had secured with his denial on Monday. Perfectly poised, betraying not a flicker of doubt about the state of her marriage, she turned on Mr Starr, accusing him of forming part of a vast right-wing conspiracy designed to torment and bring down her husband.
Had she behaved differently the game might have been up. Had she decided that, after enduring allegation after allegation of her husband's infidelity, Ms Lewinsky was the last straw; had she done the entirely irreproachable thing and walked out on her husband, then the course of history might have changed.
As it is, with the carefully weighed aforethought that marks every utterance and every gesture broadcast from the Clinton White House, she has prompted the public to conclude that her husband's behaviour cannot possibly be as bad as all that. All week, all over America, ordinary citizens have been saying, "If it's all right with Hillary, what business is it of mine what Clinton is getting up to?"
The strongest card the Clintons have is Americans' willingness to suspend their disbelief. One of Americans' defining characteristics is that they are a Utopian people. Possessed of the conviction that anything is possible if you work at it with enough of a will, they believe in the perfectibility of life on earth. That's what the American Dream is all about.
In such a scheme the unstated rules are that the President must incarnate an impossible ideal of rectitude and nobility. Or if he doesn't, you pretend that he does. The glaringly obvious fact Americans have chosen to ignore about him is that he is a serial adulterer. Mountains of evidence exist to demonstrate that he has broken his matrimonial vows repeatedly and with vigour. Yet such is the desire to believe otherwise that, save for the screamers on the rabid right, few have been troubled by his predilection for preaching abstinence from sex, drink and cigarettes to the nation's youth.
It seems, in other words, that if President Clinton has this habit - to use a favourite buzzword in Washington these days - of "compartmentalising" things in his brain, of keeping his private persona in one box and his public one in another, then the American public has been doing much the same thing. They have been tacitly colluding with his hypocrisy.
Hence the general willingness to pretend that the President did not enjoy sexual relations with Ms Lewinsky when obviously, in one way or another, he did. The evidence is overwhelming. How else to explain the 20 hours of secretly taped conversations in which she confessed all to a false friend? Or her lawyer's desperate attempts to obtain immunity for her from prosecution for perjury, from the prospect of jail, when the only statement she made under oath was an affidavit she gave Paula Jones's lawyers on 7 January denying a sexual relationship with the President? Or her visit to Mr Clinton at the White House on 28 December, one of at least 20 visits she made after leaving the White House staff for a job at the Pentagon in April 1996? Or that on the evening of 7 January she was recorded by the television cameras giving the President a big, familiar hug and then, on 8 January, the President's best friend, Vernon Jordan, recommended her for a job at Revlon, on whose board of directors he sits? How, if she is the flakey little twerp that some Clinton aides are now making her out to be, was she recommended by the White House for a Pentagon job which involved access to top-secret documents? And, finally, how else to explain the uncharacteristically flustered, unconvincing denials the President gave the first two times he was questioned on air about the alleged affair?
The public is aware, not so deep down, that the President is lying. But such is its despair to deceive itself about the President's true nature, combined with its anxiety at the thought that by destroying him it might somehow reverse the economic gains of recent years, that its latest impulse has been to turn against the news media, whose job it is to unearth the very facts it wishes to ignore. What the reporters on the President's trail fail to grasp is that, as far as the public is concerned, the issue is not even whether Mr Clinton lied or not. It is about whether he can help sustain the pretence that he did not lie, whether he can succeed in feeding the public the necessary measure of plausible deniability.
THE PEOPLE do not ask for much. All they want is to be protected from evidence so irrefutable that his guilt simply cannot be denied. Much the same could be said about the attitude of the majority of black Americans towards OJ Simpson after he was accused of murdering his wife. In each case the delusion that their hero is innocent of all charges is so cherished that they would rather lie to themselves than confront the shattering reality that it is he who is the liar.
Mr Clinton would not be the master manipulator that he is if he did not have an instinctive understanding of this impulse: that most of the people have to be fooled all of the time. But he also understands that he has no reason for complacency. As the evidence of his recent vicissitudes once more confirms, the peril that will dog him this week, and every week for the rest of his presidency, is that one day the missing clue will turn up, depriving the public of the chance to continue pretending with a straight face that he is the morally whole leader myth requires.
Should Kenneth Starr or some other American Poirot inescapably demonstrate that the emperor has no clothes, or that he cannot restrain the impulse to shed them when nature calls, then the shocked sense of betrayal will swiftly give way to an irresistible clamour for vengeance. Mr Clinton's survival rests on his ability to stop that mood from taking hold, to keep the public sweet. He is very good at that. It is what he does, with the active complicity of his ever-loving wife and loyal friends, better than any politician in the world.