Bill Clinton's biggest strengths have always been negative ones. He is not a man of great principle. He made a mess of his great political crusade to give the United States a decent and equitable health service. On issues that demand moral courage, the death penalty, say, or the defence of the living standards of the poor, he has always chosen the easiest paths.

He is certainly the most conservative Democrat to hold the presidency in the modern era. But, and this is his overwhelming personal and political virtue, he is not a rightwing Republican. And this, in the end, is what has saved him. He has been incredibly lucky in his choice of enemies.

As the impeachment process whimpered off stage at the weekend, Americans were coming to terms with a bizarre paradox. Bill Clinton has transformed American politics, not by his courage, his intelligence or his statesmanship, but by his lust, his stupidity and his moral cowardice. By fumbling around with Monica Lewinsky in the bathroom behind the Oval Office, by failing to control his compulsive sexual desires, by slithering away from the truth for as long as he possibly could, he has accomplished an astonishing political feat.

Without setting out to do so, he created a trap into which the Republican right plunged with uncontainable enthusiasm. Now he walks away sniggering, leaving his enemies up to their necks in the mire, having inflicted more damage on American conservatives with his moral weakness than a thousand liberal heroes could do with their moral strength.

The right-wing Republicans made the fatal mistake of believing their own propaganda. A belief that they are the majority, that they speak for the decent, moral American mainstream has always been crucial to their psychological make-up. Their mental world is divided between the liberal "elite", the media, Hollywood, Jews, 1960s weirdoes, gays, pot-smokers, draft-dodgers and the Moral Majority of Christian churchgoing, hard-working, respectable families. This is not an entirely foolish assumption. For one of the extraordinary things about the US is that it has bucked the trend in Western societies of becoming steadily less religious. In 1997, the Gallup organisation replicated a poll on American religious attitudes that it has conducted in 1947. The figures are almost unchanged. Ninety per cent of Americans still pray; 96 per cent believe in God; 42 per cent attend a religious service every week; 63 per cent sometimes say grace before meals. And Americans feel pretty holy. In another 1997 poll, 87 per cent said that they expected to go to heaven, compared with 79 per cent who thought the same of Mother Teresa.

So the notion that right-wing Christian fundamentalism represented the American mainstream was superficially plausible so long as it was not put to the test. As a vague assumption about how Americans like to see themselves, it could support a powerful political agenda but as a statement about reality, it is hopelessly simplistic.

It ignores three basic facts. One is that there is a huge gap between belief and behaviour: people seldom live up to their own religious ideals. Another is that Christian fundamentalism doesn't always translate into right-wing politics: most blacks, for example, are both evangelical Christians and political liberals. And the third is that religious Americans certainly don't look to politicians for moral leadership. They don't believe (rightly, as it happens) that craw-thumping Republicans are any more faithful to their spouses than pinko Democrats. They don't believe that sex is a simple or predictable business in which people obey their own moral rules.

In the grand jury testimony that he knew would end up on television, Bill Clinton made one brilliant appeal to this sense that sex is a difficult business. He referred to the confirmation hearings for Supreme Court judge Clarence Thomas, who was accused of sexual harassment by Anita Hill. Thomas and his accuser gave opposite versions of the same events. Clinton said that watching the hearings, "I believed they both thought they were telling the truth. This is what you're dealing with, in some ways, the most mysterious area of human life".

The problem with the Republican plot against Clinton is that, unlike mainstream American attitudes, it left no room for that mystery. It assumed that ordinary Americans make no allowances for the no-man's-land between what people would like to be and what they know they are.

The Republican zealots (and independent counsel Kenneth Starr must be counted among them), assumed that Clinton could be driven from office by shame and humiliation. They thought that ordinary voters could not bear to think of Clinton's pathetic need for gratification, or to picture their President as an overgrown schoolboy pleasuring himself in the White House toilets. The voters, they thought, could not help being so disgusted that their sheer revulsion would overwhelm all political judgment.

Clearly, however, the voters could help it. While much of the media and of the political elite continues to work from a narrow notion of what is and is not acceptable to the general public, a new moral majority has been emerging, not just in America but in most Western democracies. It is not, as conservatives would characterise it, decadent, amoral or so mesmerised by consumerism that it can't be bothered to distinguish right from wrong.

But it has lost faith in saints and heroes. It has given up on the illusion that there is such a thing as a perfect human being and that if we can only find these people and elect them to office, everything will be OK. It hopes for moral rectitude but doesn't necessarily expect it. It is glad of goodness, but is not automatically contemptuous of failure. It is, oddly enough, rather taken with the old religious ideal of hating the sin but loving the sinner. And it has somehow concluded that morality is not the same as self-righteousness, that tolerance and compassion are moral virtues too.

The irony is that it is the right-wing Republicans who have forced the majority of Americans to align themselves with this more open, more ambiguous notion of public morality. Starr's inquisitorial demeanour and flagrant abuse of power scared them. The stunning hypocrisy of the House Republican philanderers who set themselves up as moral arbiters disgusted them. The hijacking of the political agenda by an increasingly obsessive crusade alienated them. They were forced to admit that there are more important things than sexual morality. And that admission has cut the ground from under the right-wing crusaders. It has turned the Moral Majority into a Puritan Minority.

And that, ironically, will almost certainly be Clinton's most enduring achievement. His survival has not given him a positive mandate, and he emerges from his annus horribilis a much-reduced figure. He may, in the next two years, achieve some of his more modest political goals, preserving the social security and Medicare systems. But he lacks the authority to carry through any more radical vision.

What he will do is leave his enemies in disarray. In the course of exposing his own weaknesses, he also exposed theirs: the hypocrisy, the authoritarianism, and the fanaticism of a Republican party that tried to exploit the Christian right and has ended up being controlled by it. Simply by surviving, he has changed the American political landscape.