One of the main reasons George Bush won the US presidential election was that people trusted him, they thought him honest. Among American voters who cited honesty as the most important quality in a candidate, two thirds thought that Bush was more honest than John Kerry.

This is very odd; for, whatever we may think about the Iraq war, one thing we know is that Bush gave dishonest reasons for embarking on it. As Kerry said time and again during the campaign, the president "misled" the country into war.

Indeed, Bush went on insisting that Saddam Hussein possessed weapons of mass destruction even after it became clear that he had none. He also allowed Dick Cheney to go on claiming links between the Iraqi dictator and al-Qaida after even the CIA had said there was no evidence for it.

In contrast, Kerry generally told the truth. Yet he was the candidate most Americans found untrustworthy.

There is only one conclusion to be drawn from this, and it is a depressing one. It is that, to be trusted, an American politician has only to appear honest: if he can manage to convey the impression of trustworthiness, then he can lie with impunity as much as he wants.

Both George Bush and his soulmate Tony Blair give the impression of burning, almost messianic, sincerity, even when they are not telling the truth. One difference between the two is, however, that the president has managed to hold on to his reputation for honesty while the prime minister has been rapidly losing his.

The Americans are an amazingly religious, God-fearing people. A third of all voters in last week's presidential election identified themselves as evangelicals, according to surveys of voters as they left the polls. For them, it would seem to be enough for their president to be God-fearing as well. So long as they feel that the decisions taken in the White House are being guided by the Almighty, they are confident that nothing much can go wrong.

And Bush is a genuinely God-fearing president. There is no reason to doubt it, even if his God seems to us to have some pretty curious priorities - firearms for everyone, tax cuts for the rich, the suspension of civil rights, and so on.

The important thing for many Americans is that their leader should be acting under divine inspiration, and Bush is so convinced that he is doing so that people believe him. In these circumstances, even lies and deceptions may be forgiven if they are assumed to be necessary for the achievement of some greater good.

Tony Blair is not so lucky, for the British do not look for divine inspiration in their leaders. In fact, they are troubled by it. They loved Blair when he seemed to be a decent, open, pragmatic fellow, but began to have doubts about him as he became more mystical.

Their disillusionment grew with what appeared to be his increasing reliance on intuition rather than pragmatism. "When I was young, I paid more regard to intellect than judgment," he once said. "As I've got older, I pay more regard to judgment than intellect." He seemed to be turning into George Bush.

Unlike most Americans, the British were increasingly disturbed by the gap between their leader's obvious belief in his own sincerity and his frequent economy with the truth. They just couldn't make sense of it.

As a result, they trust Blair less and less. A YouGov poll last month found that he enjoyed the trust of only 36% of the electorate - still slightly more than the Conservative leader Michael Howard, but substantially less than Gordon Brown, who is trusted by 45% of voters.

Geoffrey Wheatcroft, in an article about Blair for the Atlantic Monthly, an American magazine, has joked that he may be an Antinomiam, a follower of a 16th-century heretical sect that believed that "to the pure, all things are pure". In other words, they believed that, because they themselves were pure, they could do any revolting thing they wanted and still be certain of salvation.

If this were true, it would explain all sorts of weird things about Blair that we find discomforting - for example, his unashamed admiration for the rich, his addiction to free holidays at their expense, and his repudiation of the traditionally modest, understated role of the British prime minister.

Bush seems like an Antinomiam, too, but, as the presidential election proved, he can get away with it.