By Caroline Wyatt
BBC News, Paris
Paris was the scene of joy and despondency on Sunday
All the opinion polls predicted it, but last night nobody in France could quite believe it -
55% of voters in this normally Europhile nation resoundingly rejected the European Union constitution.
The glum faces of the governing UMP and opposition Socialists - who all backed the treaty - were in stark contrast to the street celebrations of the motley "No" campaign. The alliance was an unlikely group of the far left, the far right and rebel Socialists.
Their supporters of all ages joined together in jubilation at Place de la Bastille, the scene of an earlier French revolt. Their impromptu street party was only slightly dampened by the rain.
"This is a message to Europe," said one middle-aged man as he toasted the "No" campaigners' victory with a bottle of red wine.
"In 1789 we were the first country to remove our royalty, so maybe it's the beginning of the new Europe, beginning today in France."
The woman standing next to him agreed: "I hope this will be a the start of a new project for a more social Europe."
Others here insisted this was not a vote against Europe.
"It was a pro-European no," said one young man.
"We are not against Europe - we just want a different kind of Europe."
But will the treaty now be renegotiated, as no campaigners hope?
President Jacques Chirac appeared to suggest not.
He was grim-faced as he addressed his rebellious nation from the Elysee Palace.
He said he respected the French people's decision, but warned them that it would make it far harder to defend French interests in Europe.
Yet this result was as much a rejection of President Chirac and the French political elite as a rejection of the treaty itself.
There is anger in France over 10% unemployment and a stagnant economy, while many worry that Europe is simply too big and no longer built in France's image.
The "No" campaigners' message convinced many that the treaty would enshrine an "ultra-liberal" economic approach which would bring about far harsher competition between EU nations, with French jobs migrating to cheaper eastern European workers.
Likewise, fears over Turkish entry to the EU - though not part of the constitution - became enmeshed in the passionate debate about the treaty.
The argument more often focused on France than Europe, a debate refracted through a mood of national pessimism and gloom about its economic prospects, and the belief that its much-cherished social model is now under threat.
The fact that Former French President Valery Giscard d'Estaing headed the committee that drafted the treaty made little difference in the end.
Last night's rejection of the constitution was also a bitter defeat for those other backers of the "Yes" vote - France's opposition Socialists.
Supporters were left drowning their sorrows at the party headquarters last night.
"I am so disappointed in the French people," said one young party activist.
"I shall probably go home to bed and cry - and then get up in the morning to find out how we face the future.
"It is a shame for France and for the rest of Europe."
President Chirac said that the rest of Europe should continue to ratify the constitution - though some wonder if that is still a viable proposition in the face of such a rejection from one of Europe's founding nations.
So why did French voters at polling stations across the country so roundly ignore the arguments of the "Yes" campaigners - who were backed by Brussels, all the main French political parties and most of the French media?
Political analyst Dominique Moisi says there were three main reasons.
"The people are saying 'No' to Chirac, they are expressing their fear and despair at the high level of unemployment in France, and they are expressing their reservations about Europe vis-a-vis enlargement.
"So it is the political, economic and European dimensions which have led to this result."
So has the French political elite been humbled - and will it finally listen to its people, who have delivered an unmistakeable message?
Mr Chirac has already said he will not resign - though it is widely expected that his unpopular Prime Minister Jean-Pierre Raffarin could be the scapegoat for this latest government defeat.
Political jockeying for that job has already begun.
The president of the governing UMP, Nicolas Sarkozy, who has made no secret of his presidential ambitions, was quick to say the government must heed the people.
"We need to listen to what the French have said. By saying 'No', the French are calling on us to call things into question deeply, rapidly, vigorously.
"The French are urging us to put an end to our failure to act, to our over-cautiousness, or quite simply to our habits, to get the country moving and to put it back into motion without delay."
The blood-letting at the French Socialist party will also start on Monday, with questions over Mr Hollande's leadership, and the actions of the rebel Socialists, led by former French Prime Minister Laurent Fabius and MP Henri Emmanuelli.
But what of the constitution itself?
The suspicion in France among the "No" campaigners is that it could be put to the French people once again - perhaps next year - so that next time they come up with the answer their political masters wanted the first time around.