There's no way of saying this without sounding a bit pretentious, but I was in Chicago a couple of weeks ago. And the most instructive person I met may have been a frail old black woman in a newsagents, who picked up a newspaper with a photo of Barack Obama on it, and thrust it under my nose.
"See him," she said, "He's in town today – Barack Obama, in town today." And she had such a gleam of pride I wondered whether he was her son. When you're used to British politicians this behaviour seems staggering. Supposing you were the most imaginative person in the world, creator of award-winning science fiction full of planets run by giant centipedes and made out of beetroot, you still wouldn't be able to imagine anyone gleefully grabbing a stranger and saying "She's in town today – Hazel Blears," even if she was their daughter.
So when Obama meets Gordon Brown next week it's going to make Brown feel even worse. Maybe Obama will advise him "Gordon, you need to come up with a snappy three-word slogan that sums up your demeanour, the way I did with 'Yes we can'." And as a result the Labour Party's slogan for the next election will be "Where am I?"
But Obama's appeal might not be just a trick of slogans and charisma. It could be that he makes statements such as "I believe change does not happen from the top down, it happens from the bottom up. Dr King understood that. It was those women who were willing to walk instead of ride the bus, union workers willing to take on violence and intimidation to get the right to organise. Arguing, mobilising and forcing elected officials to be accountable – that's the key."
Compare this to his rival John McCain, whose campaign slogans include the powerful "As President, I promise to put America first." And then his supporters all cheer, as if they're inspired, because he might have opted for "As President I promise to put New Zealand first. Bollocks to America, that place sent me to Vietnam to get tortured."
McCain's latest campaign advert begins "For some, 1968 was the summer of love. But not for John McCain, as he was in Vietnam fighting for his country." You'd think that most people, having taken that route, would spend the rest of their lives going "You'll never guess what I did in 1968 – instead of making love and listening to Jimi Hendrix I went off to drop napalm and get my fingernails pulled out –what a knobhead."
They certainly shouldn't boast about it and suggest it means they're the right person to make vital global decisions.
So the hope attached to Obama is exhilarating. Across Harlem, where almost every cafe has huge pictures of Malcolm X and Martin Luther King, they now also display an "Obama '08" poster. Conservative America despises this sentiment, so websites and radio shows are packed with stories of how you can tell Obama hates his country, because there's a picture of him not saluting the flag or dressed as a North Korean missile or something.
By the time of the election there'll be adverts saying "Senator Barack Obama claims to love his country. Yet several witnesses say they saw him trying to disrupt the first moon landing by hiding in the Sea of Tranquility and letting down the tyres on Apollo 9."
But there's an unease amongst many of his supporters, especially now that his foreign policy team includes Madeline Albright and Warren Christopher, who were the most militaristic members of Bill Clinton's government. And Obama's adviser Richard Danzig has proposed employing Robert Gates, Bush's senior supervisor for the wars in Iraq and Afghanistan.
Now his commitment to remove troops from Iraq within 16 months is dependent on "Talking to the commanders on the ground." It's not quite such a strident call for change, to say "I will bring the troops home – unless the commanders fancy staying, obviously, in which case we'll leave things as they are. But mark my words, if they decide to flee I certainly won't stop them."
The reason for all this may not be personal weakness, or even electoral fear. Because most of America will be run by the same people no matter who wins the election – the oil companies, WalMart, Murdoch etc. And Obama has set out not to disrupt their rule but to manage it. But the hope he's unleashed may not be so easily controlled, because change does not happen from the top down, it happens from the bottom up.
Or, as articulated by the topical American programme The Daily Show, "A disease is spreading across parts of the nation called 'Baracknophobia', meaning 'fear of hope'. But the disease is so contagious it's even spread to Barack Obama, who is becoming afraid of himself."
For rolling comment on the US election visit: independent.co.uk/campaign08