By Kevin Connolly
BBC News, Washington
In modern America Twitter and Facebook and live-blogging have suddenly made 24-hour cable television seem so last century.
Mr Obama ended his speech with a Churchillian flourish
Across this new electronic landscape, the headlines about Barack Obama's congressional address were being written before the final draft of the speech went off to the printers at 3pm.
Polling of people who had not heard the speech but may have picked up snippets on the internet told us that they had high expectations of it.
Before Mr Obama's motorcade had left the White House, people were reacting to the tone of his undelivered speech.
It would be sober, we were told, but with an uplifting quality to it as well, to show that he had listened to critics who had started to feel that his recent attempts to convey the gravity of the crisis have been just a little too gloomy.
There was, as it turned out, nothing wildly inaccurate about those early indications - but they failed to come anywhere close to conveying the power of the occasion, to the force of argument deployed and the strength of the emotion with which it was greeted.
There was an extraordinary standing ovation as Mr Obama made his way to the podium across the crowded floor of the chamber that refused to die down as he stood acknowledging the cheers and preparing to speak.
It seemed to me to combine a number of different strands.
There was, to be sure, a partisan quality to it in one respect - the most enthusiastic applause came from Democrats relieved that one of their own was finally in charge at the White House.
It was not, I should say, one of those soaring flights of oratory we heard from Barack Obama after the primaries of Iowa or South Carolina
But it seemed to draw its strength from other - nobler - emotional fuels too.
In part it was a legislature saluting the extraordinary achievement of an African-American man in winning the presidency.
And it was also a nation in crisis uniting behind the leader to whom it falls to find a way forward.
At times it was hard to believe that Mr Obama was a relative newcomer in a room filled with political veterans.
He has acquired a presidential authority with extraordinary speed, aided by a demeanour which even on the most nerve-wracking nights in the hardest of times is extraordinarily cool and unflappable.
It seemed too that Mr Obama has sensed that many Americas are frightened by the depth of the current recession and bewildered by the speed with which it descended.
This felt like an attempt - and a convincing one - to persuade them that he has fully understood the crisis, and can see a way ahead.
It was not, I should say, one of those soaring flights of oratory we heard from Barack Obama after the primaries of Iowa or South Carolina or on the day he won the presidency.
It was an elegantly written narrative of how America worked its way into its current state of crisis, a clearly-argued prospectus for how Mr Obama thinks it can work its way back out, and a ringing appeal to the traditional American values of hard work and innovation.
Mr Obama is sometimes accused of being professorial in tone, but he seemed to me to do a good job of explaining how the financial system arrived at the brink of collapse, not sparing some American people from their share of the blame: "People bought homes they knew they couldn't afford from banks and lenders who pushed those bad loans anyway."
That is a good, if familiar, description of how the sub-prime mortgage crisis infected the global financial system, but where I thought Mr Obama's speech was particularly effective was in going on from there to explain why he is proposing to use taxpayers money to bail out those self-same banks.
Mr Obama received numerous standing ovations during his speech
He knows that is not popular, but equally, he knows that you will not see any signs of life in the American economy until the lifeblood of credit is once again flowing through its veins.
That means helping banks, even if the American people currently feel more like kicking out their bankers than bailing them out.
As Mr Obama summed up his argument: "It's not about helping banks, it's about helping people."
There was plenty of detail in the speech about the need for healthcare reform, and green energy - big campaign themes on which Mr Obama now plans to legislate and a nod towards foreign policy too.
On Iraq, where America still has a huge and costly military operation, there was little detail but this intriguing pledge: "I will soon announce a way forward in Iraq that leaves Iraq to its people and responsibly ends this war."
And the overall tone of the speech to the wider world was positive and clearly designed to signal a break with the diplomatic style of the Bush administration.
The buzz phrase was: "A new era of engagement has begun."
Here too, as with the economy, Mr Obama knew where the applause was to be found, and he did not hesitate to go looking for it.
The speech was frequently punctuated with standing ovations - none more enthusiastic than when he declared simply: "It is time for America to lead again."
It was elegant and precise rather than dramatic for the most part, but it finished with a Churchillian flourish about letting our children's children remember that in response to the crisis of 2009, Americans did something "worthy to be remembered".
You might almost say that of this speech too - that in its reassuring approach to the exercise of the presidency it was worthy to be remembered alongside the oratory that helped win Mr Obama the job in the first place.