Obama's generation missed the sexual revolution of the 1960s - he was six in the Summer of Love. But they were in a prime position to watch the Boomers go wrong. They absorbed echoes of Woodstock, Vietnam, the social dislocation, with parents, perhaps, like Obama's mother, who were caught up in the heat of the time. They experienced first-hand the chaos of old certainties being torn apart. Then they watched the anti-establishmentarians become the establishment, and sniffed it for the phoniness it was.

McCain could have made a virtue of his age, as the anti-Boomer. Instead he made the fatal mistake of running as the "maverick".

The only way McCain was going to get people enthused to vote for a cranky 72-year-old with a croaky voice and various pre-TV quirks, such as saying "my friend" repeatedly, was to convince them he was the stable, sunny Gipper type, with all the answers amid economic uncertainty. But he has turned his virtue into a liability by mistaking non-conformity for youthfulness and vitality.

There is no room in life for a 72-year-old maverick. At 72 you should have figured out the world, and not still be railing against the guys that run it. He should not have abruptly suspended his campaign when Wall Street went into meltdown. He should not have sung "bomb, bomb Iran". These are not the marks of a dependable elder statesman, but of a man who can't discipline himself.

Obama, on the other hand, is all discipline.

In his autobiography, Dreams From My Father, he describes the shock, at nine, of seeing a magazine photograph of a man who had chemically lightened his complexion to look like a white man.

"I felt my face and neck get hot. My stomach knotted; the type began to blur on the page. Did my mother know about this? … I had a desperate urge to jump out of my seat … to demand some explanation or assurance. [But] by the time my mother came to take me home, my face wore a smile and the magazines were back in their proper place."

The dangerous Obama his opponents have painted does not align with the Obama we see on YouTube, when he talks respectfully for six minutes to "Joe the plumber".

Nor does it gel with the Obama who emerges in his book, with its brutally honest portrait of his father, the Kenyan student who met his white mother at university in Hawaii, and left a year after his birth.

In high school, he lived with his grandparents in Hawaii, where: "I was engaged in a fitful interior struggle … trying to raise myself to be a black man in America."

He would find himself talking about "white folks [and] I would suddenly remember my mother's smile, and the words … would seem awkward and false".

There's another aspect of Obama's personality that adds to the sense older people have that he is ill-defined and aloof. He is a "transit lounger" - a phrase coined in 1997 by the writer Pico Iyer to describe a globalised generation. "We pass through countries as through revolving doors, resident aliens of the world, impermanent residents of nowhere. Nothing is strange to us, and nowhere is foreign. We are visitors even in our own homes …

"We become professional observers, able to see the merits and deficiencies of anywhere, to balance our parents' viewpoints with their enemies' position … Fervour comes to seem to us the most foreign place of all." It reinforces Obama's generational identity. If it is not place that defines you, it is time.

The cri de coeur of the Obama Bunch is "Marcia Marcia Marcia". Jan's agonised complaint about her big sister embodies the gen X response to the Boomers - why does it always have to be all about them? Well, maybe it just isn't any more.

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