US saying goodbye, George and hello, President Obama

History only rarely damns a politician to his face, however. And as Mr Bush will be well aware, revisionism has worked wonders for several post-war predecessors. Already his allies, such as remain, are attempting to describe Iraq as a belated success, and to argue that this President, while sometimes inept, got the essential fact - the urgency of the war on terror - exactly right.

Mr Bush himself still seems to believe his response to 9/11 will be his vindication. That seems odd to those of us who remember the day and the stunned, baffled, inert figure clutching a children's book as the second World Trade Centre tower was hit.

It seems odder still to remember the President who denied allowing torture when the White House was sanctioning its use; who can even now make Iraq's dead generations sound like a price worth paying. The last, unfunny Bushism, indeed, is the entirely unproven claim that the Baghdad "surge" has succeeded and that all will be well. The simultaneous failure even to attend seriously to Afghanistan, ultimate source of the 9/11 attacks, is a problem left, it seems, to Barack Obama.

Amid this was the sustained attack on the rule of law in the US itself, the assault on its liberties, extraordinary rendition, the erection of a security state covering half the world and a grotesque act of presumption called Guantanamo.

Illegality can be argued over. Laws can be rewritten or reinterpreted (a habit of the Bush White House). But most of the "enemy combatants" dragged off to Cuba, more than 500, have been released without charge. The US is attempting to scatter, or conceal, the rest across the world. So what was achieved? Mass radicalisation in parts of the Muslim world? The creation of a new generation of enemies?

All American presidents have their woes, even those who sought a peaceful life. It is not required, equally, that such leaders should be virtuous: even the great Franklin Roosevelt was a slippery character, and ruthless. The task is to defend the constitution and the country, and to get the job done, whatever it might be.

History is no fixed, impartial thing. Opinions alter; historians have prejudices; reputations rise and fall. Harry S Truman tends to be held up as the nobody who became a somebody, the man who did not flinch at the prospect of an inevitable Cold War, and the President who prevented Korea from becoming a bigger mess than it might have been.

Yet might not history also remember him as the single leader in human history (thus far) to have sanctioned the use of nuclear weapons? Mr Bush never came close to that. Dwight Eisenhower, rendering his country dull but extraordinarily prosperous, governed under the "umbrella" of mutually assured destruction, of the cities to which he might, at any time, lay waste.

Mr Bush's failure, of intelligence, alertness and response, was one horrific attack on Manhattan. The saintly John F Kennedy, by comparison, came closer than any President to a full-scale nuclear war with the USSR. Perhaps the most overrated holder of the office - his legacy, particularly on civil rights, cannot be found in his record - he tipped the US into the early stages of Vietnam. If numbers of American dead must be counted, Mr Bush's wars do not compare.

Lyndon Johnson struggled with Vietnam. It finished him. But if Mr Obama's promise of "hope" matches the Great Society or LBJ's civil rights legislation, history might well be summoned. Mr Bush, with his tax cuts for the very rich, has no bearing in that debate. On the other hand the departing President was not, or never quite, Richard M Nixon.

After eight Bush years many will find it hard, perhaps, to accept, but Nixon was worse, if by a whisker. Yet what does history say these days? In the US, in particular, the President who conspired against the country's constitution, bombed Cambodia flat, whose paranoia and taste for lawbreaking were unmatched, is all but rehabilitated. The crook visited China: a triumph. Perhaps Mr Bush is right; there is hope for his reputation.

Was he as inept as Jimmy Carter, as inarticulate as Gerald Ford, as devious as Bill Clinton? Easily. Carter made the attempt, nevertheless, to bring order and decency to America's relationship with Israel. Mr Bush's last act is to sponsor the Gaza slaughter.

Say what you like about Ford, meanwhile - most did - but he would not have treated the aftermath of Hurricane Katrina as a minor municipal difficulty. Among the many indictments of Mr Bush is that, too often, he has seemed to have no clear idea of his duties or responsibilities. The Bushisms amuse, and Gerry Ford was always worth a laugh, but for eight years we have witnessed a President experiencing difficulties in carrying off the role of human being.

The mangled speech is not a key symptom. Apparent stupidity in a world leader fails to explain the sheer oddness of the man. Ronald Reagan spoke his lines clearly even while in the early stages of dementia. If Reagan appeared ignorant, that was the result of notorious laziness. Yet Mr Bush can seem oafish when compared with Reagan and his own, wooden, bumbling father.

He is mysterious. Several US journalists have alleged medical conditions without providing proof. The best you can say is that Mr Bush has appeared consistently, happily, out of phase with the world, letting the Dick Cheneys and the Donald Rumsfelds construct and conduct policy.

And the "legacy"? Many hundreds of thousands dead, the near destruction of America's moral standing in the world and an economic collapse that will consume the world for a generation. Bill Clinton, Mr Bush's immediate predecessor, had no moral standing of his own but understood a security threat and for eight years guaranteed "the economy, stupid". He lied to a grand jury and still achieved poll ratings, on quitting office, of which Mr Bush can only dream in vain.

A truly bad President, then, if not quite the worst. A man with a sort of moral autism possessed of a lethal conviction that he was always right. A man who put the world in danger while claiming to keep it safe. A man still boasting of the strength of the US economy when America, along with the rest of us, was going bust. History has its work cut out.

A controversial past George Walker Bush was born on July 6, 1946. He attended Phillips Academy, an all-boy private school in Andover, Massachusetts. Bush graduated from Yale in 1968 with a bachelor's degree in history. He enlisted in the Texas Air National Guard in May of that year.

Five years later, in 1973, he transferred to the Air Force Inactive Reserves, completing his six-year service obligation in 1974. In 1973, he attended Harvard, earning an MBA. He founded Arbusto Energy (later Bush Exploration), an oil exploration company, in 1977 with investment from many of his father's close friends.

l Bush ran unsuccessfully for the House of Representatives from Texas's 19th Congressional district in 1978. After financial difficulties, Bush Exploration merged with Spectrum 7 Energy Corp in 1984. The deal made Bush chairman and chief executive of Spectrum 7. He joined the board of directors of Harken Energy in 1986 after it bought Spectrum 7. Bush purchased a share of the Texas Rangers baseball franchise in 1989, serving for five years as managing general partner. In 1990, he sold more than half his shares in Harken Energy a week before the company announced losses of $23.2m. He was cleared of allegations of insider trading after an investigation by the Securities and Exchange Commission. He was campaign adviser on his father George HW Bush's unsuccessful re-election campaign in 1992 and went on to serve as the 46th Governor of Texas from 1995 to 2000. After a controversial election he was sworn in as the 43rd President of the United States in January 2001. He was re-elected for his second term in 2004.