Under section 17 (b) iv, the socalled "Clinton Indestructibility Amendment to the Political Pundits (Smart Arses, Know-Alls, and Assorted Puffed-Up Ponces) Act 1991, it is a statutory offence to begin this obituary without the pre-emptive disclaimer: "Barring a miracle..."

The amendment briefly fell into disuse in January when, after her disastrous showing in the Iowa caucuses, Hillary was hubristically written off. Nemesis struck three days later with The Miracle of the Coffee Shop Lachrymals, and after New Hampshire no one has dared ignore 17 (b) iv again. So then...

Barring a miracle, it ends for Hillary early next Wednesday (our time) with the release of the exit polls from Texas. It could even end a few hours before that, should Barack Obama win Ohio. But that's an even money contest, whereas he is a red-hot 1-3 favourite in Texas. This is the state Bill himself said she must win to stay in the race, and God have mercy on him if she doesn't because Hillary will be needing a scapegoat, and there's only one winning candidate for that post. She might have to sew them back on first, but among the multiple personalities she's unveiled of late there must be room for a seamstress.

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During the past 10 days, Hillary has been changing from role to role with bewildering speed. She concluded one TV debate, in what was mistaken for a valedictory, by saying she was deeply honoured to share the stage with Obama. While the audience rose to cheer her, the poll numbers rose to cheer him. So the next day she did a total volte face, and scolded him harshly for dirty campaigning ("she who smelt it, dealt it" coming to mind here).

You had to admire the chutzpah, but it didn't help, and nor did her next performance as victim of wicked media bias. Then the campaign took a stroll down Karl Rove Avenue, raising the Muslim sleeper issue by releasing that snap of Obama in Somali tribesman gear, and that bombed too. Currently she is veering between new but wildly unfocused attacks and repeating the trite bletherings (Ready On Day One, and so on) that haven't exactly enthused the electorate so far.

You'd need a heart of diamond-coated tungsten not to laugh, because even now that the obese soprano is audibly gargling her scales backstage, Hillary still doesn't comprehend how it's gone so wrong. The US media is less baffled, ascribing it primarily to electoral history's worst campaign since Noah ran for the Ararat House of Representatives on the "I'll keep the sun shining!" ticket, and you can hear the sharpening of scalpels from 3,000 miles away as the pathologists of the East Coast commentariat prepare to dissect her mistakes in the autopsy.

Yet I suspect the real story might be simpler than an amalgam of complacency, financial recklessness, Bill's unrelenting idiocy, arrogant sense of entitlement and all the rest. Could it be that she was in fact an extremely strong, if charmless, candidate who had the wretched luck to meet a rival of such transcendent brilliance that the nomination, and very likely the Presidency, was decided the moment he entered the race a year ago? That no one alive could have beaten him?

Before Iowa she had made only one fairly minor mistake (equivocating weakly over illegal immigrants' right to driving licences), and she campaigned flawlessly there and spent an untold fortune. So when Obama crushed her, no wonder everyone assumed that 17 (iv) b had been repealed, and that she could be safely written off.

If the ensuing miracle in New Hampshire seemed her resurrection then, it looks with hindsight like the twitching of a corpse on the end of a hangman's noose. Unfazed by that shock, Obama did what Hillary has failed to do by refusing to panic and sticking remorselessly to his message. It is this steadfastness, I think, more even than the elegiac oratory, that is the root of his extraordinary political talent.

The nascent backlash against him is the inevitable reward for becoming presumptive nominee, and more crowded by the hour is the bandwagon that wants to crush him by portraying him as Messianic faker, a hybrid of evangelical preacher and common grifter selling the snake oil of false hope to the needy, credulous and mildly deranged. And it's true that excitable youths sometimes faint at his rallies, while some showbiz folk talk use unnervingly religious language about him.

What is quite untrue is the implication that he is a Johnny-Come-Lately to the stirring idea that, in a democracy, lasting and significant political change must come from the bottom up. "It's time for politicians and other leaders to take the next step and to see voters, residents, or citizens as producers of this change," he says. "The thrust of our organising must be on how to make them productive ... how to create businesses, institutions, banks, safe public spaces – the whole agenda of creating productive communities. That is where our future lies.

"The right wing talks about this, but they keep appealing to that old individualistic bootstrap myth: get a job, get rich, and get out ... Our goal must be to help people get a sense of building something larger. The political debate is now so skewed, so limited, so distorted. People are hungry for community. They miss it."

These quotes aren't from a recent stump speech or conference call. They come from an interview published in the Chicago Reader on 8 December 1995, before he was first elected to the Illinois Senate. For a dozen years and more, then, Obama has been astoundingly consistent. If the language has become more lyrical, the belief has stayed the same, and electors instinctively sense that constancy and integrity. On a gut instinctive level – and ultimately how else are races decided? – they know he means every word. This is why Hillary's attempts to denigrate him as a slick charlatan are so futile.

It could, of course, turn out that the Obama formula of using poetry to rouse the grass roots to do the prosaic things required to improve America will prove naive fantasy. In almost five years from now, or preferably nine, history's snap verdict may very well be "No we couldn't." But on Wednesday he will at least be one huge step closer to putting that theory to the test, and the Lord be thanked on bended knee for that.

For Hillary, nothing remains but to pray that Obama loses to John McCain so she can try again in 2112 (and with that in mind, expect an amazingly gracious withdrawal speech on Wednesday). As far as the odds, the prediction markets, the polls and the demographic movement behind those polls, all she can do now is read 'em and weep.

And weep she surely will, probably late on Sunday in time for the networks bulletins on Monday morning, Doomsday Eve. It worked for her once, but not again. Not twice within a few weeks. Barring a you-know-what.