The victory for the Yes campaign was a dark day for democracy, according to a number of No campaigners.
"Irish voters have succumbed to threats, pressure and bamboozlement by their political class," said Mr Anthony Coughlan of the National Platform. "The Republic's Yes voters have thereby shown that in Ireland at this time it is the Government, not the people, who are the masters."
MEP Ms Dana Rosemary Scallon said: "I am most saddened by the damage to the democratic process. We came back to vote on the same treaty. It is a dangerous precedent to set."
When asked for his reaction Mr Justice Barrett of the No to Nice Campaign said jokingly: "We lost, damn it! Is there much else to say?"
He added that the "full weight of the establishment bore down on people, and produced the result at the end of the day.
"They succeeded in characterising the core issue as whether we are in the EU or not. That was not true. They did it with broad brushstrokes, and that was the essence of their message."
However, the size of the No vote was very creditable in the circumstances, according to Mr Coughlan. There was a vast imbalance in resources with the Yes side spending 20 times as much as the No side.
This was combined with the "gutting" of the Referendum Commission last December, when legislation was rushed through in one day on the eve of the Dáil rising for Christmas, Mr Coughlan said.
This meant the commission could no longer set out the pros and cons of the issue as they had in the first Nice referendum. The resulting material, produced by an advertising agency, was not fair and balanced, he said, and he would be producing a full analysis of this in the coming days.
Despite this defeat, the No campaigners are not going away. "If anyone is thinking of saying goodbye to us, they'd be better to use the French au revoir," said Mr Barrett.
"The Yes campaigners this time got away with not showing where the EU is going. The long-term programme is a federal state. They will not be able to pretend otherwise in the next referendum.
"I would like Ireland not to be isolated in having a referendum next time.
"I believe Jacques Chirac has made a commitment that there will be a referendum in France on any constitution. That would be very good. I think we will be revisiting the European issue very quickly."
Ms Scallon agrees. "We politically endorsed the European Charter by voting for the Nice Treaty," she said. "You cannot isolate Nice from what is going on around it, which is the establishment of Europe as a political and legal entity."
AfrI and the Peace and Neutrality Alliance opposed Nice from the opposite end of the political spectrum to Dana and Mr Barrett, and in their reactions both emphasised the peace and neutrality issues raised in the campaign.
Mr Roger Cole of PANA said: "It was a magnificent result for us given the enormous amount of money spent by the Yes side. The total number of No votes held up."
He said a "major factor" in the campaign was the disclosure of Mr Justin Barrett's links with a far-right elements in Europe.
"A significant element wanted to show their disapproval of Mr Barrett and his attendance at a Neo-Nazi rally, and I congratulate them for that if that was their reason for voting Yes."
In a statement AfrI said that the issues raised have not gone away. "Irish and EU foreign policy is, increasingly, developing a military dimension.
"The version of neutrality that has been placed in the Constitution is, unfortunately, a red herring. It rules out Ireland joining a defence pact without a referendum, but does not prevent us joining in offensive operations outside the EU with the European Rapid Reaction Force."
ireland.com's Nice referendum website offers a comprehensive guide to the issues with continuing news, reaction and analysis of yesterday's result.
The site features interactive maps and quizzes with a chronology of European integration, profiles of the applicant states and the full text of the treaty and related documents.
Nice Referendum 02 can be accessed at: www.ireland.com/focus/nice/