I don't write much about America. This newspaper boasts reporters and commentators with so much better knowledge and wisdom in this field that my three-ha'pence-worth seems superfluous. It's years since I was at university in Connecticut and my finger is no longer anywhere near the pulse of Washington politics or American culture.

So this column, provoked by the suspension of Hillary Clinton's campaign, will be an unusual trespass into unfamiliar territory. It is written by a comparative ignoramus and complete outsider.

But maybe it's worth venturing a view from the outside. While very hesitant indeed about Barack Obama, and pretty incredulous about John McCain, I feel as an Englishman the strongest possible impulse to wish both well - and to wish well the idea of America that they might embody. It is not an impulse I could have felt so strongly toward Senator Clinton or Mitt Romney, two eminently capable and decent politicians of whom I know no ill.

What is it about Senators Obama and McCain that inspires this particular British commentator to see them as men who might meet America's need at this moment in the nation's history? To answer, I need a word that takes us on from where my colleague Daniel Finkelstein left his column on Wednesday - with the sentence “Who soars, wins”.

The word is nobility. America is more than a country: it is an idea. How the world sees the idea of America matters not just to the world, but, increasingly, to America. The idea of America thirsts for a reinforcing shot of nobility. Only a president can provide it.

Somebody, I suppose, has to care whether Mrs Clinton is best placed to win the blue-collars or the Hispanics; or whether Mr Obama can extend his appeal beyond blacks and liberal intellectuals; or whether Mr McCain should balance his free-thinking reputation by choosing this or that individual as running-mate. But if Americans would raise their eyes beyond socioeconomic groupings to the horizon, they might see something huge and worrying in prospect. It is the loss of their nation's honour in the world; and they should ask themselves how and where they will find a president to secure and bring it back to them.

I used the word “nobility”. In political communications we have endured a great deal of keyword strategy-mongering over the past decade. Vision. Hope. Dream. Reform. New. Inclusive. Compassionate. And, ever and again, Change, Authenticity, and Feel Your Pain. These are cool, modern, buzzy concepts, and you may think “nobility” out of place among them: an old-fashioned concept with elitist undertones. Like all the primal human qualities the word eludes definition except in its own terms; but we know what it means. It includes ideas of dignity, of unself-interestedness, of largeness of spirit, and of a rising above spite, faction and greed.

Justifiably or otherwise, this element of nobility has been a strong strand in the legend of America. I could argue that the reality has often departed from the legend and that qualities such as nobility should be attached to individual human beings rather than to nations. But whether legend or fact, few would deny that the idea of nobility has been important to the way that the United States has seen itself, and the way we outsiders have seen the United States. I don't think that the Statue of Liberty represents an entirely hollow idea, or that the words “Give me your poor, your tired, your huddled masses...” are without resonance. Or that they and the exalted spirit animating them could easily be attached to the name of any other nation on Earth.

Nobody should (and I don't) represent the history of the United States as the continuous triumph of altruism and principle. I wouldn't even claim the preponderance of those qualities. But they do, if fitfully, appear to recur: a sort of trademark for America. Rightly or wrongly, names such as Washington, Jefferson, Lincoln, Wilson, Truman, Roosevelt, Kennedy - even, abroad, Carter and Clinton - would, put to any multinational focus group, test positive for perceived moral stature not just as domestic politicians, but as figures in world history. I would argue for the inclusion in that list of Ronald Reagan, too - there was something big about the old man; just as there seemed to be an air of decency surrounding George Bush Sr. Put in the fashionable terms of 21st-century marketing, there has persistently been something noble in the American brand.

I wonder whether most Americans have understood in how parlous a condition this version of America now finds itself abroad. Seen from outside, the essential nobility of the American ideal is close to shattering. The American Eagle, as we abroad see the creature, looks sick - perhaps mortally so.

I wonder, too, whether most Americans, or the cheerleaders on this side of the Atlantic for the present Republican Administration, have understood the urgency as well as the depth of this crisis for the American brand. During George W. Bush's first term I argued on these pages that he and his friends risked imperilling something more valuable to America than Iraqi deserts. This risk is now close to tipping over. International opinion always hungers for ogres and America is in imminent danger of being cast in that role. Across the free world, the Soviet Union appeared for decades in the guise of World Enemy No1. In June 2008, the US is not far from feeling that yoke descend upon its shoulders. It's a heavy yoke to bear, for once it settles, everything a nation does is seen by outsiders through the prism of that country's supposed ill-intentions.

We could argue about whether this would be fair. I would say not. We could argue too about whether neoconservatism is essentially ignoble. Again I would say not: Kennedy's foreign policy (“bear any burden, pay any price...”) can be seen as neoconservative before the name was even invented. Instead I would maintain that no particular policy, and no particular individual - even George W. Bush - has alone threatened the idea of American nobility, but that a malign combination of events and people, including McCarthyism, the Vietnam War, three terrible assassinations, Watergate, Iraq, Guantanamo Bay, men such as President Bush, Donald Rumsfeld and Dick Cheney, and attitudes to global warming, has conspired to threaten the legend.

In the way that Americans do politics, one person stands head and shoulders above all else in defining the nation to itself and the world. That person is the president, and it is personal. Not just in what he does but in what he is or seems to be, a president can make America feel and look a nobler idea. I happen to think that both Mr Obama and Mr McCain are distinguished from the other would-be candidates by conveying, in their speech and in their personal histories, an idea of nobility. I wonder whether in some subliminal way those voting in the primaries sensed this, and sensed its importance. I hope so, and that in the campaigns ahead both candidates can do what eagles do - soar.

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