America's belief in the institution of its presidency is extraordinarily resilient. For over 200 years, the leaders of the United States have sinned and subverted their way through history and the people have forgiven them, even loved them for their peccadillos. Times do change. The Presidency is not as invulnerable as it once was. The sexual antics of a John F. Kennedy would not be tolerated today, not because the public is more or less puritanical than it was in the early 1960s, but because the Washington establishment, especially the media, are no longer prepared to pass over presidential misbehaviour in silence. Yet Bill Clinton, for all the allegations of sleaze against him, is one of America's most popular presidents. It is not that dirt does not stick. He is no 'Teflon president'. All recent polls show the majority of Americans believe he did have a sexual relationship with Monica Lewinsky, the White House intern. Few are ready to believe his denials of this affair any more than those of previous allegations by women purporting to have been seduced or propositioned by him. He may be telling the truth. Equally, he may not. The point is, he is not believed. But the public does not seem to think, this week at least, that sexual shenanigans should lead to his downfall. This is strange in a society that has hounded and brought down so many others over allegations of sexual harassment and rather subtler behaviour than Mr Clinton appears to go in for. But it does seem, for the moment, that Americans accept that presidents live by a different moral code to the rest of us. There is an implicit acceptance that the kind of man hungry enough for power to make it to be president of the world's only superpower may be hungry for dominance over women. He has plenty of antecedents on that front. Kennedy and Mao Zedong are but two examples. (Powerful women might have the same urges to dominate men sexually, but one wonders if Americans would be so accepting if it were a fictional President Hillary Rodham Clinton's private life which were being splashed over the media and not her husband's). Instead of worrying about his affairs, the public is more sensibly concerned with whether Mr Clinton is doing a good job. And, once again with that caveat 'for the moment', it has not found him wanting. The presidential machine has capitalised ruthlessly on this peculiar tolerance. It has set out to destroy the character of the woman at the centre of the controversy as it has of the colleague who spilled the beans. It has rounded on the Independent Special Prosecutor, Kenneth Starr and portrayed him, possibly not entirely without reason, as politically biased and determined to destroy the President whatever the evidence. It has managed to co-opt the President's own wife into suggesting that Mr Starr is part of a great right-wing conspiracy against him. It has called into question the very justification for a Special Prosecutor's Office, despite the fact that, without one, there would be precious little scrutiny of the President's actions and probity while in office. And it has, with a good deal of carefully stage-managed muscle-flexing and global swagger, managed to persuade at least part of the American public that it should concentrate its righteous wrath on the Iraqi dictator Saddam Hussein, not on its own president. Mr Clinton has, in short, made one of those political comebacks for which he is so famous. No longer the only target of attack and innuendo, he has taken the offensive and made his opponents look bad for questioning his integrity. He has even managed to win the admiration of much of the US establishment, the international community and some of his bitterest detractors for his ability to compartmentalise. He makes a fine show of concentrating on the affairs of state without letting his legal battles or the affairs of his heart and other organs interfere with daily management of the nation. All this could change again, overnight. If it can be proved that he lied, or that he warned Ms Lewinsky to lie about their relationship, public opinion could quickly turn against him. Rightly so. Sexual harassment and adultery are not admirable behaviour in a president, but they do not rank with lying to the country and suborning witnesses as grounds for impeachment. Mr Clinton's integrity has never been much believed in by the American people. But to be caught red-handed in lying and persuading another to perjure herself on his behalf would destroy whatever credibility he has left. All presidents make mistakes and some commit crimes. Some have done so repeatedly. All have probably been involved in cover-ups. But few have been as brazen about it - or as transparent - as Bill Clinton would then appear to have been. In such circumstances, impeachment could not be ruled out.