Yet the "No" vote also rose, from 529,000 in the first poll to 534,000 in the second, indicating a solid underlay of public opposition to European initiatives.
That, combined with the current hostility to the EU among Irish farmers and dissatisfaction with it among some of the business community, is worrying senior government officials.
"The Irish Farmers' Association (IFA), who are hostile to world trade talks involving the EU, have indicated that they will vote "No" if there is no improvement in the EU's position, while many business bosses are concerned over the EU's meddling in corporate tax," said one.
Paradoxically, EU funding has been a major contributor to a booming Irish economy since Ireland joined the bloc in 1973, with Irish farmers in particular receiving hunderds of millions of euros under the Common Agriculture Policy.
But Irish farmers are angry with EU Trade Commissioner Peter Mandelson's handling of world trade talks, fearing they will be the big losers in any deal. Irish business leaders oppose moves towards a common EU corporate tax rate.
COMPELLING ARGUMENTS
Sources within the IFA, which represents nearly 100,000 farmers, also did not rule out campaigning for a "No" vote. One said: "We hope the situation improves, because otherwise there will be a backlash."
"It would not be in anybody's interests to hold the treaty hostage for other issues, but this referendum will require all the political parties, trade unions and business leaders who believe in this treaty to get behind it," Roche said.
As in France and the Netherlands two years ago, Roche said Eurosceptics from around Europe would focus their efforts on supporting the "No" campaign in Dublin in the coming months.
Analysts also highlight the risk that extraneous issues could overshadow the debate over the new treaty, which provides for a long-term president, a strengthened foreign policy chief and more say for European and national parliaments.
"Neutrality, taxation, immigration, enlargement and WTO could all come into play," said Brigid Laffan, research director of the Dublin European Institute at University College Dublin.
"Referendums are a one-off "Yes" and "No" vote on a complex issue so the political environment at the time is key."
