You can measure the scale of an American president’s troubles by the number of skutniks he deploys during his State of the Union address.

Every year during his big set-piece speech to Congress, the president will digress from the main thrust of his remarks to offer fulsome praise to some member of the audience in the gallery. This person will have been carefully selected in advance by the president’s speechwriters as an exemplar of some virtue and placed there for the purpose. The television producers will have been alerted in advance so that at the right moment, as the president talks about the heroics of this American Everyman, he or she can rise self-consciously and receive the praise of a grateful nation. This now obligatory part of a constitutional ritual is called a skutnik after the name of the first person so honoured.

One January evening in 1982, Lenny Skutnik, a government employee, dived into the freezing waters of the Potomac River to rescue a victim of a plane crash. Two weeks later, during his second State of the Union address, with the US mired in recession, Ronald Reagan had Mr Skutnik sit in the gallery and paid a moving tribute to his heroics.

This week, for his penultimate State of the Union, Mr Bush had a veritable galaxy of skutniks — soldiers, military people, a firefighter. Whatever you might feel about the wisdom of Mr Bush’s Iraq policy or the feasibility of his plans to wean Americans off petrol, you can’t help but stand and cheer the good works of a decent person.

But there was something unusual about this year’s constellation of ordinary American heroes, beyond the sheer numbers. Usually the skutnik is a presidential privilege. But so intense already is the competition for the 2008 presidential race that others have muscled in.

And so Senator Hillary Rodham Clinton had a skutnik of her own. She arranged for the son of a New York policeman sick with lung cancer to be there. As it happened, the man’s father died that day, and the son’s grief became a sad and very visible coda to the event.

This little incident, the skilfully choreographed exploitation of a human tragedy, the cynically manipulated deployment of public sympathy in service of a personal political end, offered a timely insight into the character of the politician who this week launched the most anticipated presidential election campaign in modern history.

There are many reasons people think Mrs Clinton will not be elected president. She lacks warmth; she is too polarising a figure; the American people don’t want to relive the psychodrama of the eight years of the Clinton presidency.

But they all miss this essential counterpoint. As you consider her career this past 15 years or so in the public spotlight, it is impossible not to be struck, and even impressed, by the sheer ruthless, unapologetic, unshameable way in which she has pursued this ambition, and confirmed that there is literally nothing she will not do, say, think or feel to achieve it. Here, finally, is someone who has taken the black arts of the politician’s trade, the dissembling, the trimming, the pandering, all the way to their logical conclusion.

Fifteen years ago there was once a principled, if somewhat rebarbative and unelectable politician called Hillary Rodham Clinton. A woman who aggressively preached abortion on demand and the right of children to sue their own parents, a committed believer in the power of government who tried to create a healthcare system of such bureaucratic complexity it would have made the Soviets blush; a militant feminist who scorned mothers who take time out from work to rear their children as “women who stay home and bake cookies”.

Today we have a different Hillary Rodham Clinton, all soft focus and expensively coiffed, exuding moderation and tolerance.

To grasp the scale of the transfiguration, it is necessary only to consider the very moment it began. The turning point in her political fortunes was the day her husband soiled his office and a certain blue dress. In that Monica Lewinsky moment, all the public outrage and contempt for the sheer tawdriness of it all was brilliantly rerouted and channelled to the direct benefit of Mrs Clinton, who immediately began a campaign for the Senate.

And so you had this irony, a woman who had carved out for herself a role as an icon of the feminist movement, launching her own political career, riding a wave of public sympathy over the fact that she had been treated horridly by her husband.

After that unsurpassed exercise in cynicism, nothing could be too expedient. Her first Senate campaign was one long exercise in political reconstructive surgery. It went from the cosmetic — the sudden discovery of her Jewish ancestry, useful in New York, especially when you’ve established a reputation as a friend of Palestinians— to the radical: her sudden message of tolerance for people who opposed abortion, gay marriage, gun control and everything else she had stood for.

Once in the Senate she published an absurd autobiography in which every single paragraph had been scrubbed clean of honest reflection to fit the campaign template. As a lawmaker she is remembered mostly, when confronted with a President who enjoyed 75 per cent approval ratings, for her infamous decision to support the Iraq war in October 2002. This one-time anti-war protester recast herself as a latter-day Boadicea, even castigating President Bush for not taking a tough enough line with the Iranians over their nuclear programme.

Now, you might say, hold on. Aren’t all politicians veined with an opportunistic streak? Why is she any different? The difference is that Mrs Clinton has raised that opportunism to an animating philosophy, a P. T. Barnum approach to the political marketplace.

All politicians, sadly, lie. We can often forgive the lies as the necessary price paid to win popularity for a noble cause. But the Clinton candidacy is a Grand Deceit, an entirely artificial construct built around a person who, stripped bare of the cynicism, manipulation and calculation, is nothing more than an enormous, overpowering and rather terrifying ego.