By Stephen Mulvey
BBC News, Amsterdam
The Dutch Socialist Party was already geared up to celebrate a victory for the "No" camp before the exit poll flashed up on the television screen.
But when it appeared the crowd went wild.
The reasons why the Dutch voted 'No' were many and varied
The margin of 26 points appeared to be at the upper end of expectation.
Immediately, the No Constitution Rap, theme tune of the "No" campaign, blasted out and the Socialists danced.
The gist of the song is this: "If you want a social Europe, and a Europe for the people, not for business and money, then say 'No' to the constitution."
Thinking for themselves
Some voters evidently did want a social Europe, and voted "No" for that reason, but many others said "No" for quite different reasons.
Christian Democrats (CDA), largest government party, plus coalition partners VVD and D66
Labour (PVDA) and Green Left opposition parties
Right-wing Pim Fortuyn party
ChristienUnie and SGP, Christian parties
The television screens looming above the party-goers were showing a live programme from Hilversum. Right-wing "No" campaigners periodically appeared - the maverick MP Geert Wilders for example, whose main theme during the campaign was opposition to immigration and Turkish membership of the EU.
On the streets of Amsterdam, people were giving varied arguments both for and against the constitution.
This may be because neither the "No" side nor the "Yes" side has been putting forward one coherent message, but the people have also been thinking for themselves.
One person talks about the euro, the next about domination by bigger EU states. Another will talk about Brussels bureaucracy, or the threat to Dutch liberal values, or loss of sovereignty and national identity, or the motor of European integration speeding out of control.
A common complaint is that Brussels does not listen.
"I am very pleased at this result and not because I am against a united Europe," says Lydia Meist at the Socialist Party celebrations.
"It's because of the whole way things were managed, manipulated, not just by our government, but by the authorities in Brussels. The arrogance! Being so sure of themselves without speaking to the people of Europe, deciding for themselves!"
Campaigners for the "Yes" vote are also rueing the fact that Dutch citizens have not been asked to vote on EU policy before.
"The message from France and the Netherlands is that they are unhappy with the way Europe is being built," says Michiel van Hulten, a leader of the Better Europe foundation and a former MEP.
"People are unhappy with the fact that Europe is a project of the elite, not the ordinary people.
"The decision to introduce the euro was taken in 1992 in Maastricht, but at the time there was no public discussion. The enlargement of the EU was agreed in 1993, but it was only when it actually happened that the debate began."
Separating out all these reasons for the "No" vote and ranking them in order of importance will be a major undertaking.
France and the Netherlands in 2005 clearly have some things in common, including a poorly performing economy and a deeply unpopular government - in the Dutch case, the most unpopular government on record.
Some of the arguments heard in both countries have been the same.
Many Dutch said they were worried that the EU is expanding too fast
Some, on the other hand, have been the opposite - French voters lamented their country's diminishing power, while Dutch voters were more likely to complain that the big countries, mainly France and Germany, were too strong, and would become stronger under the constitution.
It is also clear that the French "Non" fuelled the Dutch "Nee".
"Vive la France," says Daniel de Jongh of the Constitution No [Grondwetnee] group in the Netherlands.
The French vote, she says, undermined in one stroke the Dutch government's argument that the Netherlands would be isolated if it rejected the constitution.
The scale of the French "No" vote also made clear that it was not only nationalists and chauvinists who were opposed to the constitution, she says, and that centrists and left-wingers could vote against it without finding themselves in company they would normally shun.
She acknowledges however that both left and right in the Netherlands have tapped into a deep-seated dissatisfaction with the country's main political parties - which all supported the constitution - and a widespread feeling that they are not listening to the voters.
The late Pim Fortuyn was the first to do this, achieving huge popularity within months of setting up his anti-immigration party, the Pim Fortuyn list.
Now the constitution "No" campaign has built on his anti-establishment legacy.