Writers who have made a close study of George W. Bush are baffled at how he is now launched on what may be a successful campaign for the White House.

He has never been very ambitious. He has been something of a playboy figure for most of his life. And, unlike his Democratic rival, Al Gore, who hungers to be president, Bush says he is prepared to lose and go back and live a normal life with his wife Laura, twin daughters, dog and three cats at his ranch in a desolate part of Texas.

Bush never actively sought to be the Republican candidate until a poll in 1997 while he was serving his first term as Governor of Texas showed that he was the frontrunner. His father's name had much to do with this sudden emergence on the national political stage.

Republicans who had seen their candidate, Bob Dole, humiliated by President Clinton in the 1996 election were desperately looking for a winning name when Clinton would have to stand down in 2000.

There was still anger at how a governor from a redneck state like Arkansas had taken the White House from Bush's father, a second World War hero, a former head of the Central Intelligence Agency, envoy to the UN, ambassador to China and the president who led the US and its allies to victory over Saddam Hussein in the Gulf War.

When President Bush was defeated in 1992, his son, who had not been active in his campaign, was said to have been devastated. One biographer says that he took up running "to blunt the pain". It was "the Bush tonic for sadness, for the crushing disappointment of defeat".

Newsweek this week has Bush and his running mate, Dick Cheney, on the cover with the caption "The Avengers", but Bush does not accept this view. "You can't win an election if your reason for running is based on revenge. A leader has to be an optimistic person," he says.

He has always had a sunny, optimistic outlook, according to those who have known him over his 54 years. Early life was in the oil town of Midland, Texas, where his father was trying to make it in the oil business.

When Bush was only seven his three-year-old sister, Robin, died of leukaemia. He tried to cheer his parents up with jokes and pranks, a friend recalls.

When he was 15, his father decided that it was time for his son to go east, follow in his own footsteps and enter Phillips Academy in Andover, Massachusetts - perhaps the most exclusive prep school in the country. Bush emerged with middling grades but was noted for his gregariousness.

He may not have had his father's patrician bearing and high-achiever drive inherited from the renowned Senator Prescott Bush of Connecticut pedigree, but the young George had the gift of mixing easily and making strong friendships.

Then came Yale, where the father had excelled as a student and became captain of the baseball team. For the son, Yale in the 1960s was more a fun time with much partying and beer-drinking but only average grades and no sporting achievements. There was a run-in with police for making off with a Christmas wreath and wrecking goalposts at Princeton after a Yale victory.

After Yale, Bush was liable to be drafted to fight in Vietnam but he somehow ended up flying F-102s in the Texas Air National Guard with virtually no chance of being sent overseas. His father almost certainly pulled some strings to get his son this slot. Bush says now he regrets not going to Vietnam.

Then came some aimless years in Houston as Bush toyed with politics but mainly had a good time. He once lurched up to a respectable matron to ask "What's sex like after 50?" After a night's drinking at Christmas 1972 in Washington where his parents had moved, Bush challenged his father to fight mano a mano, his biographers relate.

His parents were relieved to learn that he had been accepted by Harvard Business School.

After Harvard, Bush was still unsettled and returned to Midland in Texas, the scene of his boyhood. Again, it was a period of partying, drinking with friends and dating.

His boyhood friend, Joe O'Neill, recalls that Bush used to drive a banger, wear second-hand clothes and live in a room over a garage. O'Neill says: "We were all in our 30s. We were the young and the useless. We didn't have a lot of money, but we had a lot of fun." Then Laura Welch, a pretty Methodist librarian and schoolteacher, entered Bush's feckless life. He was 32 and had decided to run for Congress, but lost. Within three months he married Laura and was working in the oil business - not very successfully.

The social drinking continued until Bush's 40th birthday when he suddenly decided to give it up. He had also had a religious turning in his life after a discussion with evangelist Billy Graham at the Bush vacation home at Kennebunkport.

Bush dislikes talking about this experience, but says "It was the beginning of a new walk where I would recommit my heart to Jesus Christ." Some friends believe that the birth of twin girls, Barbara and Jenna, in 1981 also brought a new maturity to his life.

After helping his father get elected president in 1988, Bush returned to Texas where he switched from oil to baseball and raised $600,000 for a minority stake in the Texas Rangers. When the team was sold in 1998, Bush found himself $15 million richer.

Four years earlier he had become Governor of Texas after defeating the incumbent Democrat, Ann Richards, in a race few thought he could win. As governor, Bush reached out to the Hispanic minority population, using his familiarity with Spanish.

He also formed an unusual alliance with his Democratic deputy governor, Bob Bullock, and the two men worked together to push through reforms in education, an area in which Bush is passionately interested.

In 1997, Bush was so popular that he was re-elected with 67 per cent of the vote, which included half of the Hispanic vote that would normally go to the Democrats. No wonder the Republican establishment started looking south to Texas for a new standard-bearer, and millions of dollars poured into a campaign which had not even been announced.

Bush's record in Texas has been scrutinised by friend and foe to see what it reveals about the real man behind the back-slapping bonhomie. He is a fervent upholder of the death penalty and has presided over 135 executions in six years without any regrets, but his power in the area is limited to granting a temporary reprieve.

His record in areas other than education is deeply conservative and marked by special treatment for big business. However, he wears his conservatism lightly and tries to leaven it with Christian precepts. This approach has now been neatly encapsulated into his presidential campaign as "compassionate conservatism".

But the commentators and the writers still puzzle over what is behind the facade of a man who would not be on the trail to the White House if his name were not Bush. What does he believe and why does he believe it? When asked why he is running he replies: "It's not just holding office for the sake of holding it. The reason is to keep the economy growing, to keep the peace."