KEY POINTS:
He is black. He delivers a great speech, a bit grandiloquent and humourless, but great. What else?
Well, he's nice. Truly nice. When this week's show-stealer, the wholesome "hockey mom", turned out to have a slight family dysfunction, he said: "My mother had me when she was 18."
He didn't need to say that, although unfailingly nice would seem his wisest tactical response to Sarah Palin. Coming from nowhere to centre-stage, she is going to captivate the campaign for a little while, until everyone remembers she is running for vice-president.
Once they are ready to return to the main game, he needs to be ready with something new and substantial. Oratory alone is starting to pall.
The Republican convention gave him a hint this week, making fun of his previous job in Chicago, "community organiser". Hurricane Gustav gave him another hint.
New Orleans is a black city, and a mecca of one of the distinctive American musical cultures that transcends racial hostility and gives the whole country a point of pride. And the city may be dying.
I was there in December 2006, nearly 16 months after Hurricane Katrina. Descriptions of its condition last week suggest not much has changed. Reportedly a third of the flooded districts have yet to regain half their previous population.
I saw vast suburbs of what had been modest, mostly black communities lying much as the floodwater had left them. Street after street of dank, deserted houses still wore high water lines on their weatherboards and marks left by emergency services that indicated, among other things, whether people had been rescued or bodies removed.
Many of the evacuated owners had found work where they went and simply stayed there. Those that had come back were still camped in their front yards in white caravans supplied by the Federal Emergency Management Authority.
Electricity leads ran from the caravans into the dead houses.
Residents had contemplated the costs and effort needed to restore their house to a state of minimal comfort. Their problem was not so much a want of loan money and energy. Suppose they put in the money and effort, dried the timbers, relined and refurbished the rooms, cleared the debris from their yard, cut the grass and made it liveable again - and nobody else did.
Would the neighbours make the same effort? Would anybody? How many in the same street might go to the trouble? Who wants to own a pleasantly restored house in a derelict street? How many restorations would be needed to reach a critical mass at which a community could survive?
All this I gleaned on a bus tour guided by a genial midwesterner. In one devastated area he remarked that those living there had been "not just black people", seemingly oblivious to the skin tone of the pleasant couple across the aisle. They had been quietly answering questions for me that he had not understood.
New Orleans, it was clear, didn't lack citizens who loved it and had the will to restore it, but they were in a classic prisoner's dilemma. They couldn't do what they individually wanted to do because they couldn't do it collectively.
City and Federal Governments were blaming each other for maladministration of relief programmes but you had the sense that at heart America does not conceive social solutions, even in an emergency. Barack Obama, by the sound of him, does.
New Orleans is an extreme case of the prisoner's dilemma you see in black communities all across America. The districts are dilapidated. Nobody would do up a house in those neighbourhoods. Anybody who can make any money moves.
Obama is not just black, he seems outside the American mainstream in other ways. His Kenyan antecedents and Hawaiian upbringing appear to have given him a cultural reach that Americans, black and white, generally lack.
It was not just star quality that made Europe embrace him on his recent tour. I think John McCain could restore America's respect in the world; I know Obama would.
For Americans, the plight of New Orleans ranks up there with Iraq and the economy in the indictment of Bush. But in the land that prospers on individual enterprise and personal responsibility there is still a reluctance to recognise that sometimes communities need help - maybe as much help as the financial community has received from the Federal Reserve and Treasury this year.
If I was advising Obama's campaign I'd have him get down to New Orleans with a daring proposition applicable to all of America's social blight. Time and place are right, Gustav is the first good fortune the city has had in years. The water was whipped up and the repaired levees held.
Now it needs nothing so much as a community organiser.
