Bush was born to baseball as he was to so much else. His grandfather had batted fourth in the 1917 Yale baseball team, and his father, the future President Bush, captained Yale's championship winning side, played in the 1947 College World Series, and was once even approached by a scout.

In baseball as in so many other spheres, the younger Bush lacked his father's talent. His mother Barbara remembers him as 'the most enthusiastic player', while his father wrote that 'Georgie' is 'so eager. He tries very hard.' George W himself says his happiest memory is playing catcher in little-league coached by his father in Midland, Texas.

He was a better fan than player. Even today he can name the 1954 New York Giants starting line-up by heart, writes one of his biographers, JH Hatfield. In his youth he sent SAEs to baseball stars asking for their autographs, went with his father to watch the Houston Astros, and to the New York Mets with his great-uncle Herbert Walker, one of the team's original owners. Owning a baseball team was perhaps Bush's first realistic career goal.

As a freshman at Yale, he pitched for the baseball team. Later he would recall the day the team's manager took one look at him warming up in the bullpen and told the second baseman to pitch instead. 'And that was the end of my career.'

Instead he made his main mark on Yale sports as a fan. After the college's American football team - of which he was elected 'chief cheerleader', though he never mentioned this in later political campaigns in macho Texas - won a match at Princeton, he and some fellow students decided to celebrate by removing the Princeton goalposts. They were arrested by campus police but released minutes later. Bush now classifies this with all his other youthful misdemeanours under the rubric 'young and irresponsible'.

After college he turned to golf. At Midland Country Club in the Seventies a prize for worst-dressed golfer was awarded in his honour, reports Hatfield. But baseball was to be key to Bush's political career. At the end of the Eighties, he was nothing but his father's son. He had achieved mediocre grades throughout an exclusive education, had drunk heavily, avoided service in Vietnam by jumping a queue for the Texas National Guard, failed to get elected to Congress, run loss-making oil companies, and worked for his father's presidential election campaign. As he admitted in 1989: 'You know I could run for governor [of Texas] but I'm basically a media creation. I've never done anything.'

This would change. A right-wing millionaire named Eddie Childs was trying to sell his baseball team, the mediocre Texas Rangers. Bush, who had little money of his own, tried to put together a consortium of buyers. Peter Ueberroth, then commissioner of baseball, who happened to be friends with the elder Bush, lent a hand. A group of 70 investors was assembled to pay $83 million for the club. Of that sum, $640,000 came from Bush. He was given two per cent of the franchise and made managing director.

What happened next is a murky episode, well told by Molly Ivins and Lou Dubose in their hilarious biography Shrub . The Rangers were then playing in a former minor-league park in Arlington. The Bush group wanted a bigger stadium. Strangely for a phalanx of right-wing millionaires, they decided that local taxpayers should finance it otherwise, it was threatened, the Rangers might move elsewhere. The people of Arlington voted to increase the local sales tax by half a per cent, thus raising the $191m needed for the ballpark.

Then things got murkier still. The 13 acres where the Rangers wanted to build the stadium belonged to the heirs of Curtis Mathes, a television magnate. They demanded $2.8m for the land. The club, however, had been granted the legal power to condemn and take land. It offered the sellers only $812,220. The matter went to court and a jury set a price of $4.2m. The Bush consortium said that should be paid not by the Rangers but, in effect, by the people of Arlington. Having condemned the private property of the Mathes family, Bush later ran for governor of Texas on a platform of 'private property'.

The Rangers years set Bush up for politics. Running the club made him a famous Texan in his own right. If Europeans are bewildered by his apparent rise without trace, this is partly because they don't follow baseball.

Bush did little at the Rangers. He controlled neither the finances nor the playing side. He did, however, officially approve all trades and it was in this department that he made one of his most famous blunders: the trade of Sammy Sosa.

In 1998, when Sosa hit 66 home runs for the Chicago Cubs, this trade looked less than prescient. Paul Begala, a consultant to President Clinton, has asked: 'Does America want a president who would trade Sammy Sosa?'

For the most part, however, Bush was merely the official face of the Rangers. He would sit in the stands handing out baseball cards with pictures of himself. It made him happy. He eventually opted for politics. Running for governor of Texas in 1994, he would constantly cite his experience in baseball. It helped that the Rangers, boosted by the income from the new stadium, had become contenders. The club won their division three times in four years. At last, George W Bush was a success.

Elected governor, he decorated his Austin office with 250 signed baseballs. Never one to let work dominate his life, Bush would still regularly appear at Rangers games, or sit with his wife on the lawn listening to the game commentary on a boom-box.

In 1998 the Bush consortium sold the Rangers to Tom Hicks for $250m. Most of the value was in the taxpayer-financed stadium. Bush netted $14.9m. 'When it is all said and done,' he said, 'I will have made more money than I ever dreamed I would make.'

When he began running for president, he could point to little working experience.

The governor of Texas is above all a ceremonial figure who cuts a lot of ribbons. He could hardly boast about his years in oil. So once again, he talked about baseball. He told the Washington Post : 'Baseball is a marketing business. It's a business of being able to relate to fans and convince fans to come out. I do build teams. That's what a president does.'

John McCain, his main opponent in the Republican primaries, a veteran senator who spent years in a Vietnam prison, imagined a Bush campaign ad based on his Rangers experience: 'But when the scouting reports come in, there is only one lonely man in a dark office.'

Yet baseball did help Bush. It fed the notion that this millionaire son of Washington is a regular guy, and suggested, falsely, that he had had a hands-on job in a multi-million-dollar operation. The link with the ultimate American game has also helped him seem ultimately American.

Bush beat McCain. Six years after leaving his job at the Rangers, he will probably be declared president. To a large degree, he owes that to his favourite sport. 'Baseball,' concluded the Washington Post , 'has been, arguably, the most important thing in Bush's life.'

That is not true. Being the son of George Bush has been the most important thing in Bush's life. But baseball comes a good second.