This was a week when William Jefferson Clinton must have wondered why he ever wanted to be President. For the past six months he has been living through a kind of hell that few other men would endure and still get up every morning to get on with their job.

Back on stage this week came the familiar faces but with greater menace as Monica Lewinsky struck her immunity deal with the independent counsel, Mr Ken Starr, and Linda Tripp finished eight days of secret testimony and told a baffled American public: "I am you".

The media feeding frenzy intensified as the White House struggled to put a favourable spin on two startling developments, Monica Lewinsky's deal and the President's reluctant agreement to testify after six months of saying No.

Monica Lewinsky is where it all began and may yet end with a disgraced Presidency. We saw Monica filmed over and over again driving to her lawyer's office with a bag said to contain the black dress she says is stained with the physical evidence of an affair Mr Clinton swears never happened.

The talk show hosts cranked up their dirty jokes, the anti-Clintonites sniggered, the President's supporters cringed. The President himself addressed conferences, shook hands, patted heads and smiled when inside he must have been in turmoil.

Hillary Clinton, who has loyally backed her man against what she sees as a "rightwing conspiracy" to destroy him, kept her head high. As she walked into a Washington restaurant tourists leaped to their feet to applaud her. And how does daughter Chelsea get through days like these as all one hears on every airwave and TV news is her father, Monica's dress and sex?

The President must now prepare for what could be the worst day of his life on August 17th, two days before his 52nd birthday, when he sits down in the White House with Mr Starr and his lawyers and is asked under oath for a second time if he had sexual relations with Monica Lewinsky. It will be seven months to the day since he sat with Paula Jones's lawyers and swore he did not.

What will he do on the 17th? Polls show most people believe that he lied last January and probably committed perjury. Even many of his own supporters believe he was economical with the truth to say the least.

Ms Lewinsky will have preceded him, and Mr Starr expects her to testify that they had sex. She would be admitting she committed perjury last January but she is now immune from prosecution unless she lies in her latest testimony.

The dilemma for the President is clear. If he repeats his denial of sex, he will be in direct conflict with Ms Lewinsky, and Mr Starr may have enough corroborative evidence to argue that the President is committing perjury a second time.

Influential quarters such as the New York Times are urging the President to "correct" his January testimony, admit he lied then, be contrite and ask for another chance so that he can get on with his Presidency.

The attraction of this course of action is that it would mean there was virtually no chance that Congress would move to impeach President Clinton. It can only impeach a president if it convicts him of "high crimes or misdemeanours". Adultery would not qualify but perjury could if it were seen as part of obstructing justice in a criminal case.

Lying about an affair when being questioned about the Paula Jones civil case, now dismissed, is not seen as impeachable even by Republican opponents. And public opinion does not see it as making him unfit for office.

The downside of "correcting" his January testimony is the effect an admission of an affair would have on the people who loyally believed the President's denial and the humiliation for himself and his family. His presidential authority would be damaged even more as the film clips of him angrily denying an affair would be played beside the shame-faced retraction.

The other choice for the President on August 17th is to reaffirm under oath that he did not have sexual relations with Ms Lewinsky. We must not forget that this may be true in spite of the evidence piling up apparently to the contrary and Ms Lewinsky's switching of sides.

The danger here is that Mr Starr may still be convinced the President is lying. Mr Starr would then presumably send a report to the House of Representatives setting out the evidence he has assembled that perjury was committed. Whatever about perjury last January in a civil action, perjury by the President before a grand jury investigating possible crimes and obstruction of justice could not be ignored by Congress with an election only months away.

That does not mean Congress would find the President guilty and force his resignation. First, the House of Representatives would have to vote to impeach and then the Senate would try the case and vote whether to convict or not.

The Republicans have majorities in both houses but they don't always vote along party lines. But neither do Democrats, and if the evidence of presidential perjury was strong enough, some Democrats would also feel obliged to vote accordingly.

If the Democrats win back control of the lower house next November, this would greatly help the President as his political allies would head the key committees and have the vital majorities.

So for President Clinton there is legal jeopardy and political jeopardy.

If he is going to stand by his denial of sex with Monica Lewinsky, he will risk a damning report by Mr Starr which will catalogue every one of the at least 37 visits of Ms Lewinsky to the White House, often on weekends and at night, backed up by testimony from Secret Service agents, secretaries and stewards.

There will be the 20 hours of Linda Tripp tapes with Ms Lewinsky's outpourings about her crush on the man she once called "The Big Creep". There will be his own phone messages on her answering machine and there may be damning evidence from the dress, although this would mean Mr Clinton had to provide blood or saliva samples which he may not be willing to do.

Mr Clinton could still escape impeachment following such a report from Mr Starr if the politicians do not have the stomach for it. Republicans may not fancy having Vice-President Gore taking over the Presidency within a year of running for the office in 2000. Better to have a wounded, humiliated Clinton clinging on as the presidential campaign hots up in 1999.

But there are a lot of "ifs". It is still important to remember that the President so far denies strongly that he had sex with Ms Lewinsky and that until she testifies it is anonymous "legal sources" who are leaking that she is going to swear, possibly next week, they did have sex.

When the President's turn comes on August 17th, he, like her, will swear to tell the truth. Americans living through a booming economy have been happy with him as President even if most of them don't believe his denial of last January. Will they continue to be so tolerant if they see him caught in a perjury trap set by Mr Starr?