Republican John McCain has completed a remarkable comeback
It was a night of drama that offered all the epic themes of Campaign 2008 in crystallised form - victory and defeat, youth and experience, and even, when it came to the Texas voting system, chaos and confusion.
For once the Republicans should have had the better story to tell - John McCain wrapped up their nomination with a string of easy victories.
But it was the Democrats who once again grabbed the headlines with another
Hillary Clinton comeback, throwing her party's race wide open once again.
Mrs Clinton won in Rhode Island and in the much larger state of Ohio (which has an uncanny knack of voting for candidates who go on to be president) - and above all, she won the popular vote in Texas.
It was a sweep of results that made a nonsense of predictions on the way in to the voting that she would be forced to withdraw from the race if she did not manage at least a couple of victories.
She celebrated with one of her best speeches of the campaign so far.
It was one of the few evenings when she was more colourful and more passionate than her rival - dedicating her victory to "everyone who's ever been counted out, but refused to be knocked out...and everyone who works hard and refuses to give up".
On the Democratic side, the night belonged to Hillary Clinton
Some of her rhetorical devices even felt as though they had been, let us say, inspired by Barack Obama.
He is fond of telling the story of a poor women who sent him a money-order for $3.01 to help him in his campaign.
Mrs Clinton now offers a mother of two little girls who sent her $10, and who wrote movingly of how she and her daughters cheer and chant along with the crowds whenever they see her on television.
It almost sounded like acknowledgement that Mrs Clinton knows she does best on days like this - when she is being written off by the media, and when Mr Obama's people are making a little too much of the argument that he is the front runner and that it is mathematically impossible for her to catch up with him in the delegate count.
It is curious that it is now Mr Obama, the poetic candidate whose sweeping rhetoric can lift huge crowds, who is left to make that rather cold mathematical argument based on the way his party uses proportional representation to choose its candidates, while Mrs Clinton revels for the first time in months in the feeling that momentum is with her.
We can make a guess at the tone of the campaign to come now, too.
Hillary Clinton 17 states, 1,592 delegates
Arizona, Arkansas, California, Florida, Massachusetts, Michigan, Nevada, New Hampshire, New Jersey, New Mexico, New York, Ohio, Oklahoma, Pennsylvania, Rhode Island, Tennessee, Texas
Barack Obama 24 states, 1,723 delegates
Alabama, Alaska, Colorado, Connecticut, Delaware, Georgia, Hawaii, Idaho, Illinois, Iowa, Kansas, Louisiana, Maine, Maryland, Minnesota, Missouri, Nebraska, North Dakota, South Carolina, Utah, Vermont, Virginia, Washington state, Wisconsin
2,025 delegates needed for nomination. Source AP (includes all kinds of delegates) Q&A: US election delegates
Arizona, California, Connecticut, Delaware, Florida, Illinois, Maryland, Missouri, New Hampshire, New Jersey, New York, Ohio, Oklahoma, Pennsylvania, Rhode Island, South Carolina, Texas, Vermont, Virginia, Washington state, Wisconsin
Mitt Romney 11 states, 251 delegates
Alaska, Colorado, Maine, Massachusetts, Michigan, Minnesota, Montana, Nevada, North Dakota, Wyoming, Utah
1,191 delegates needed for nomination. Source: AP (includes all kinds of delegates)
Mrs Clinton put Mr Obama under pressure in the last couple of weeks and it seemed to work.
Look out for a few more examples of going negative - we will soon see if Mr Obama fights back in kind or if he has a glass jaw.
It may well be that even in Ohio and Texas, Mrs Clinton shares the available delegates almost equally with her rival, but her supporters will argue that hardly matters.
For the Clinton Camp, 4 March was all about stopping Mr Obama's seemingly unstoppable progress to the nomination and denting the sense of mystique and inevitability that he was starting to develop.
The Texas Democratic voting system, by the way, is maddeningly slow to yield up its final results - the state uses a system which is jokingly referred to as the "Texas two-step" in which voters are asked to take part first in a conventional election - the primary - and then, hours later, in a long, argumentative discussion system - a caucus.
When too many people turn up, the only result you get for hours, is total chaos.
In a sense, though, the final figures are not important.
Mrs Clinton's performance should be enough to persuade any "super delegates" who were thinking of backing Mr Obama to pause for a while and to see what happens next.
Those delegates, of course, are the party grandees who make up about 20% of the votes in the nominating convention in August, and whose decisions are likely to be influenced by their sense of how support is ebbing and flowing between the candidates.
On the ground, Mrs Clinton has loyal support she can count on.
In Columbus, Ohio, I met several women who turned out and started working for her when they realised that she was in trouble - that is a huge, but strange asset for the Hillary camp, a kind of reservoir which only seems to come on stream in the senator's darkest hours.
Her strategists need to find a way of mobilising that kind of support at moments when they are already doing well.
The speculation that Barack Obama might do well enough to end the Clinton campaign made the Clinton camp's successes seem all the more dramatic and helped to ensure that the Democratic race once again grabbed the headlines.
That should not disguise the fact that this was a big night for the Republican Party and for John McCain, now confirmed as its candidate for the White House.
All this represents an extraordinary turnaround for a man whose campaign almost ran into the ground last year for a lack of funding.
The much-decorated former Navy pilot - a war hero who was shot down, captured and tortured by the North Vietnamese during America's conflict there - now has the opportunity to begin his presidential campaign.
He can also begin to beat up on his Democratic rivals while they are still beating up on each other, and that is a huge advantage.
Mr McCain will need that advantage too, if he is to overcome his two big problems.
The first is that Democrats have been raising more money and voting in much greater numbers than their Republican rivals in this primary season - and that may give a clue as to the tone of the November general election.
The second is that the conservative wing of the Republican Party does not trust his legislative record on issues like the environment and illegal immigration. On the plus side, he now has a little time to fix that and to start filling his war chest.
You can expect Mr McCain to attempt to make this an election about national security - the field in which he has a clear advantage over any Democrat rival - look out for Iraq to take centre stage in the months to come.
And which Democrat will he be facing in the televised debates to come?
The truth is, we still do not know and in the days and weeks to come we move on to Wyoming, to Mississippi and to Pennsylvania with the Democrats as divided as ever between Mr Obama's soaring oratory and Mrs Clinton's seeming unsinkable fighting spirit.