I'm writing this just after 4am, having stayed up late to watch Barack Obama accept his party's nomination as candidate for President. And I've been thinking back to the first time I watched a Democratic Party convention, exactly 40 years ago: Chicago, 1968, when there were fights, literally fights, over whether delegations from southern states should be allowed to participate because they refused to accept any black members.
Well, tonight, the Democrats embraced a black Presidential candidate. Forty years is a long time in politics.
While I was waiting for Senator Obama, I began leafing through a book that's been sitting for months on my desk.: it's called "Speeches that changed the world." And it has reminded me that speeches do sometimes matter, do sometimes make a difference.
Will Obama's speech tonight be one of those? I have no idea. But the speech he made at the Democratic party convention four years ago certainly changed his world: it launched him on a meteoric political trajectory that just might take him all the way to the White House.
And consider these:
The Conservative party leader David Cameron's speech to his party conference in Blackpool three years ago, which certainly changed his world too: it won him the party leadership , and might well take him all the way to Downing Street;
John F Kennedy's inauguration speech in 1961: "Ask not what your country can do for you, ask what you can do for your country", which changed the way Americans thought about themselves and their country, at least temporarily;
Franklin D Roosevelt, in his inaugural address in March 1933: "The only thing we have to fear is fear itself", steadying American nerves after the banking crash.
And, of course, Winston Churchill, in May 1940, as the Nazis swept across Europe: "I have nothing to offer but blood, toil, tears, and sweat."
So I could have written today about the continuing crisis in the Caucasus, or about the collapse of the coalition government in Pakistan following the resignation of President Musharraf. But I decided not to simply because, in many ways, Barack Obama's speech - and American voters' reaction to it - may well have a profound influence on developments in both Georgia and Pakistan.
My impressions of tonight's speech? There was more steel - and even more anger - than I had expected ... this was a Barack Obama grittily determined to put America back on the right track, ready and willing to attack John McCain ("it's not that he doesn't care, it's that he just doesn't get it") - and ready to strike one of the lowest blows I've heard from the man some commentators call Saint Barack: "If John McCain wants to have a debate about who has the temperament, and judgment, to serve as the next Commander-in-Chief, that's a debate I'm ready to have." (McCain has a reputation as a man with a tendency to blow a fuse.)
There was plenty of the high-blown rhetoric we have come to expect; there was the personal back-story that is a given on such occasions - but there was also a hefty dollop of detailed policy proposals (on tax cuts, health care, and job creation, for example) that many American voters probably won't have heard before.
So what the Democrats are hoping for now is a great big bounce in Obama's opinion poll ratings as they head home, and the Republicans start heading for their convention in Saint Paul, Minnesota. Even before he spoke, a was showing him six points ahead of McCain after two weeks of level-pegging. So from their point of view, the early omens are good. But of course, the same thing may well happen for McCain after the Republican convention, and then we'll all be back at square one.
Oh, one final thing: happy 72nd birthday today to Senator McCain.
I'm going to be travelling in the US for the next couple of weeks: next Friday, I'll be presenting The World Tonight live from Missouri, the bellwether state where only once in the past 104 years have they not voted for the winning candidate in a presidential election. I do hope you'll be able to tune in, either on air or online.