On a chilly November night in 2008 I stood with my camera crew in Grant Park, in Chicago, and watched the new 44th president of the United States being greeted by his ecstatic supporters.
It was a magnificent, unforgettable moment. And yet even then there was a nagging question in my mind about Barack Obama.
I'd met him briefly a few months earlier and been impressed by his intellect. I had heard several of his speeches and knew what a moving and thoughtful orator he could be.
Yet face to face I'd had a nasty feeling that he wanted me and everyone else he met to like him. And having spent much of my career reporting on strong political leaders who didn't care whether you liked them or not, I found that worrying.
Would Obama be tough enough to achieve the things he was talking about on that historic night in Grant Park?
Well, he still has two years to go, so writing his political obituary is premature.
But at this point in a two-term presidency, you can tell if it has been successful. And it's hard to imagine that Barack Obama can possibly be judged a success when he leaves office.
In a way, it's deeply unfair.
Economic judgements are always supposed to be the deciding ones for an American president, and in Barack Obama's case the judgement is clearly positive.
During the savage downturn, which has done such damage to Germany, France and Japan, the American economy has grown by more than 7% since 2008, and unemployment is now below 6%. These are serious achievements.
It's true that by some measures China's economy has just overtaken or is about to overtake the American one, but that is certainly not Barack Obama's fault.
In health care, one of the issues he spoke about at Grant Park, he has enabled millions of poor Americans to get proper health insurance for the first time.
But in the wider world, American prestige and effectiveness have dropped sharply - as sharply as under Jimmy Carter (another immensely clever and thoughtful man) and George W Bush.
The world (well, most of it) wants an active, effective America to act as its policeman, sorting out the problems smaller countries can't face alone.
It was a major mistake on President Obama's part to think that America could pull back from its historical position and not appear diminished.
And he made other mistakes. Warning President Bashar al-Asad of Syria that the US would not accept it if he used chemical weapons against his own people, and then doing nothing when it happened was a foreign policy disaster.
The growth of Islamic State is traceable to that lack of decisiveness.
And although he spoke at Grant Park about restoring America's lost moral standards after the revelations of water-boarding and other torture, this hasn't happened either.
Guantanamo Bay, which he promised to close, is still open, and the brutal force-feeding of prisoners on hunger-strike there still goes on.
The old notion Americans had of themselves as a city on a hill whose moral light couldn't be hidden has been irreparably damaged. And President Obama has done little to improve that.
Is it too late for him to turn things round now? Probably.
He could always, of course, concentrate on tackling the Israel-Palestine issue.
But the time for a two-state solution seems to be passing very fast, and may already have gone.
If President Obama tries to put pressure on Israel, he will be made to suffer heavily for it by pro-Israel groups in the US.
It's perfectly possible that after his bad start he will be able to defeat Islamic State in Syria and Iraq.
But it will take longer than the time he has left, and the 45th president, whoever that will be, will get the main credit.
Still, President Obama will be just 55 when he leaves the White House in January 2017.
Jimmy Carter, after all he has achieved in the years since he left the White House, is now one of the most respected people in America. So is Bill Clinton.
Their perceived weaknesses as president dropped away when they returned to private life, and had the freedom to do what they wanted.
George W Bush stayed at home, painting portraits of people's dogs. Barack Obama won't.
There is plenty for him to achieve. And without the huge, unreasoning, often insensate anger and suspicion that was directed at him, he may be able to do more than he could as president.
A man with so much ability deserves the chance to shine, even if he never quite managed it in office.