One of the more absorbing rituals of American presidential election cycles is the quadrennial Will He? Won’t He? parlour game.

In the early stages of the campaign (which gets earlier every four years) a smattering of anonymous hopefuls jostle with a handful of more familiar figures for the public’s attention. But for a while all the media really want to know is whether one man, whom they have anointed the most exciting Republican or Democrat in the country, will decide whether he wants to run.

In 1996 it was General Colin Powell, then merely the former chairman of the joint chiefs of staff, who was generating frenzy in the press and barely disguised alarm in the camp of the incumbent President, Bill Clinton, as the most talked about potential Republican candidate. For months General Powell let the winds of media speculation blow wildly across the sands of his supposed presidential ambitions before opting out and leaving merely an electoral desert for the Republican party.

No one, however, agonised so publicly nor teased so effectively as Mario Cuomo, the former governor of New York, whose route to the Democratic nomination in the 1992 contest had been lovingly prefigured by political professionals. Mr Cuomo famously went to the point of having a chartered plane waiting on the tarmac at Albany airport in December 1991, ready to whisk him to a formal announcement of his candidacy in New Hampshire. But the plane never took off. The Governor declined to bark and the caravan moved on.

This time, a little over a year before the first votes are cast, the man playing the starring role in the latest adaptation of The Undecided is Barack Obama.

Since he first declared in October that he was actively thinking about a presidential run, the 45-year-old senator from Illinois, the only black man in the Senate, has steadily raised the temperature. On Sunday he will fan the flames a little harder when he shows up in New Hampshire, site of the first primary contest for the Democratic nomination in January 2008. Usually, first-time candidates in the state are required to earn votes the hard way — trudging from door to door in an effort to persuade a notoriously sceptical public that they have what it takes. But such is the excitement around Mr Obama that in his first trip there the senator will simply progress from one sold-out event to another. Early polls have him vaulting to the front of the field.

There are two main reasons that the senator is generating such interest. The first is a cold, hard Democratic calculation: that he is not Hillary Clinton. Or more accurately, that he is the most appealing national figure whom Democrats see as a plausible candidate to stop Mrs Clinton from cruising to the party’s nomination.

There is a so far unproven but nonetheless deeply held conviction in influential Democratic circles, even among those who admire her, that for all the former First Lady’s formidable advantages she is simply unelectable. This conviction is matched by an equally firm belief that, as things stand, given the strength of the current likely field, and barring the entry into the race of someone with real appeal, she simply cannot be denied the party’s nomination.

Mr Obama, they think, can with one bound, release them from the prison of a Clinton candidacy. This is because of the second main reason for Obama-mania. There is something almost mystically appealing about his potential presidency — a black man from humble beginnings, whose grandfather was a Kenyan goatherd, and who got to Harvard Law School and the US Senate.

His popularity so far suggests he has real political skills to match the irresistible narrative. Though he is solidly left of centre on the tough issues for Democrats — abortion, gay marriage, gun control — he manages to appeal to the centre ground. He won election easily to the Senate from Illinois, triumphing not only in urban black districts but in leafy white middle-class suburbs.

For a nation in which race is a continuously reopening sore, the prospect of an Obama presidency is genuinely thrilling. What’s more, he actually opposed the war in Iraq too. And what better way to demonstrate to the world that America is ready to heal the tears in the fabric of international relations of the last five years than by electing someone named Barack Hussein Obama.

With all this going for him, why the uncertainty? What is holding him back? Senior Democrats whom he has been consulting in the last month or so say the cautious Mr Obama is concerned about his evident inexperience. Just two years in the Senate, Mr Obama has no legislative record to speak of. His political skills have hardly really been tested yet. In his successful Senate campaign two years ago he ran against a Republican who was forced to pull out of the race after allegations that he had abused his wife.

Obama-boosters note he is actually older than John Kennedy was when he was elected president in 1960. But when he ran, Kennedy had been in the House of Representatives for six years and the Senate for eight. He had, for good measure, been decorated in wartime too.

It might be better, some are telling Mr Obama, to wait awhile. You’re young, they say. Give it a miss this time. You’ll be a shoo-in for 2012, or 2016. But a number of Democratic senators disagree. One consulted by Mr Obama recently told him to remember there is nothing like timing in presidential politics. There are only half a dozen people in America at any time with a real shot at becoming president, he told him. When your name is among them you do not tarry.

Mr Obama talks about faith a lot, another reason he is seen as appealing to a wide range of Americans. In his second book, The Audacity of Hope, published this year, he demonstrates a detailed command of the Bible. One passage in Ecclesiastes seems composed for him: “The race is not to the swift, nor the battle to the strong, neither yet bread to the wise, nor yet riches to men of understanding, nor yet favour to men of skill; but time and chance happeneth to them all.”

For Mr Obama , the time seems to have come. Only chance awaits.

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