Johann Hari: If you really want to understand what this race is about, look at the two candidates' fathers

The Hillary-dam has finally burst, so now oceans of newsprint are being spilled over the long-delayed Republican vs. Democrat showdown. But as we simplistically blather about the candidates' race and age – it's hip vs hip operation, folks – we seem to be ignoring the best guide we have to John McCain and Barack Obama's hearts.

Both men have written strange, searching books about their fathers. It is in their pages that we can find the clearest clues to their potential presidencies. At first glance, these slabs of non-fiction – Dreams From My Father by Obama, and Faith of My Fathers by McCain – are strikingly similar. They both tell the autobiographical story of an insecure young man who flails around for an identity, and finds it by chasing the ghost of his absent father to a dangerous place far beyond the United States. Yet Obama ended up writing a complex story of colonised people – while McCain wrote a simple celebration of the coloniser.

Barack Obama Snr was a Kenyan goatherd, born into a country ruled by British white supremacists. He had watched his own father move from job to job – as chef or butler or servant – because he would not allow white men to beat him when he made a mistake or got "uppity." He saw his father disappear for six months into a British Guantanamo, because he had been (falsely) accused of being part of the resistance. All around them, some 50,000 Kenyans were being slaughtered by the British in an attempt to put down the rebellion. A favoured tactic was bursting their eardrums. Obama was offered a way out when some American aid workers saw he was smart, and helped him apply to study in the US.

There, he met Ann Durham, a poor white girl from Kansas. They quickly got married, at a time when "miscegenation" was still illegal in half of all states, and had a baby. He abandoned them in Hawaii when the baby was two, and the younger Obama only met his father once again, fleetingly.

As he grew up, Obama writes: "I was engaged in a fitful interior struggle. I was trying to raise myself to be a black man in America, and no one around me seemed to know exactly what that meant." He tried turning himself into "a caricature of black male adolescence." He tried living as a community organiser in Chicago. And – when his father died in a car crash – he tried to find it in Africa, by chasing his memory. But he discovered a father who had failed. Obama Snr. had left children strewn across the world. He had been blacklisted from the Kenyan government for speaking out against corruption; he sank into the bottle, and isolation.

It was in the slums of Kenya that Barack the son realised he was an American, tied inexorably to his country's freedoms and failings. There was no contradiction. He thought of his grandmothers – one watching her home burned down by colonisers, another hurrying at 6.30am to catch the bus to work in a bank in Hawaii – and understood: "They all asked the same thing of me, these grandmothers of mine."

The lens through which McCain views the world is radically different. He was born into military royalty, writing: "For two centuries, the men of my family were raised to go to war as officers in America's armed services." He writes of his "pride" in being descended from "the distinguished conqueror" Charlemagne.

McCain's father was mostly absent, away at sea. As a navy child, McCain writes, "you are taught to consider their absence not as a deprivation, but as an honour." But he hungrily sought out stories of his grandfather and father. They were both angry, hard-drinking men, often disciplined for starting fights: his grandfather even drank the alcohol used to fuel torpedoes on his submarine. Warring was all they knew. When the Second World War ended, his grandfather lamented: "I feel lost. I don't know what to do."

Sometimes their strict obedience to the military was put to great causes, like saving the world from Nazism. But just as often, it was used to crush democracy: in 1965, McCain's father led the invasion of the Dominican Republic to destroy the forces loyal to the elected leader and install a fascist thug. In his book, McCain calls this operation "a success".

While Obama's father and grandfather were being whipped and detained without charge, McCain was being taught to revere the people doing it. He writes of his father: "He was a great admirer of the British Empire, crediting it with keeping 'a relative measure of peace' in the world for 'someplace in the neighbourhood of two hundred years.'" This is a view his son holds to this day – as we can see from the fact that his foreign policy adviser, Niall Ferguson, calls for the US to pick up where Britain left off. He describes his own childhood in the wreckage of Obama's Snr's Kenya as "a magical time" where "scarcely anything had changed since the days of White Mischief".

But McCain feared he would never live up to his father. He too had become a fighting, drinking, bottom-of-the-class Navy brat always on the brink of being thrown out. Then, on one of his first air raids over Vietnam, he was shot down and captured by the Viet Cong. He was held and tortured. They offered to release him early, but US soldiers are told to insist on being released in the order they were captured. So he stayed for five years, and was tortured some more. In Hanoi, he writes, "I fell in love with my country". In its torture cells, he discovered he was worthy of "the faith of my fathers."

When he returned, his father told him the only problem with the war is it wasn't fought hard enough: Nixon and Kissinger should have bombed more civilians, with less restraint. (They killed 3 million.) His son still agrees: he is angry at the "utterly illogical restraints on the use of American power". McCain says of his predecessors: "I still aspire to live my life according to the terms of their approval." It's true. His father's reaction to failure in Vietnam was to urge bombing of Cambodia; his reaction to failure in Iraq is to sing "Bomb bomb bomb, bomb bomb Iran."

I do not want to exaggerate the difference between Obama and McCain. The US political system is hemmed in by vast blocks of corporate power and geopolitical pressures. Any president can only nudge this system by inches, in either the right or wrong direction – but when a giant moves by a few inches, the effect is vast.

From his father, Obama learned to eschew "the confidence reserved for those born into imperial cultures" that they should rule the world their way, with "a steady unthinking application of force". He can imagine the mentality of the boy in Basra whose father has vanished into an occupiers' prison, because it happened to his father and grandfather too. McCain learned the opposite from his father: that the natives only ever learn "to behave themselves" at the end of a big stick. So now we have to ask: which ghostly father will America choose?

j.hari@independent.co.uk

For rolling comment on the US election visit: independent.co.uk/campaign08