The Taoiseach, Mr Ahern, and other party leaders campaigning in favour of the Nice referendum yesterday urged voters to say Yes to enlargement of the EU.
In final press conferences before the election tomorrow, Yes campaigners said the Nice Treaty allowed for full participation and further development of the EU.
They also called for Yes votes in the other two referendums, the abolition of the death penalty and the establishment of the International Court of Justice, saying it was a chance for Irish people to make a statement of their commitment to human rights.
The Taoiseach said the Nice Treaty was about extending the benefits of EU membership to other countries which were ready to join so that Europe did not always remain divided as a legacy of the Cold War.
There would be huge disillusionment and disappointment all over Europe if the Irish people failed to back the Nice Treaty. Neither our present partners nor the applicant countries would be able to understand why Ireland rejected the treaty when Europe had been so positive for us, he said.
"We cannot, in conscience, pull up the ladder behind us. It would be mean-spirited in the extreme to deny the applicant states the right to share in the benefits when Ireland will still be receiving about £5 billion in net transfers from the EU over the next five years," said Mr Ahern.
An enlarged EU would lead to further demilitarisation in Europe. Ireland's neutrality was being fully maintained, he said.
The Labour Party leader, at the party's press conference, criticised the Taoiseach for the way the campaign had been handled.
Mr Ruairi Quinn said he did not believe the Irish people wished to wake up on Friday morning to meet the disappointment and devastation in central and eastern Europe that would accompany a No vote.
"The reality is that the accession of smaller states to the EU will, if played correctly, give Ireland the opportunity to maximise further its influence within the EU," he said.
The Progressive Democrats leader, Ms Mary Harney, said a positive signal should be sent to the people of central and eastern Europe about peace and prosperity.
A No vote could be seen as Ireland handing over the political initiative on its engagement with the EU to hard-left socialists, Sinn Fein and misguided Greens, she said.
The Fine Gael leader, Mr Michael Noonan, said the referendum was the opportunity to make Irish voices heard in the future shaping of Europe. The applicant countries looked on Ireland as a role model.
"Let us show a spirit of generosity by delivering a resounding Yes vote," he said.
The leader of the European Liberal Democrats, Mr Pat Cox MEP, said Ireland, uniquely, had the choice to exhibit solidarity with the candidate states.
The Minister for Foreign Affairs, Mr Cowen, welcomed Mr John Hume's support for Nice and said his endorsement was a step of considerable importance.