A seismic shift in the politics of the island of Ireland will be revealed when the result of the concurrent referendums on the Belfast Agreement are announced later today.
A majority Yes vote, North and South, is expected on the agreement, following the first all-Ireland poll yesterday since the 1918 general election.
But the shape of politics and the prospects for lasting peace will be determined by the preponderance of the Yes vote in Northern Ireland.
However, in Dublin, where a national turnout of around 60 per cent was estimated, there was some caution among political sources in predicting the outcome of the referendum on the Amsterdam Treaty, with speculation about the extent of the No vote.
In Northern Ireland there was an estimated turnout of 80 per cent. Supporters of the Yes campaign were expecting to get between 65 and 75 per cent of the vote, but opponents of the Belfast Agreement said the Yes vote would be no higher than 60 per cent.
An overwhelming majority of Catholics were voting Yes, with estimates ranging as high as 95 per cent. The Protestant community was said to be more evenly divided, in some of the heaviest voting on record in the North.
Queues formed at some polling stations before they opened at 7 a.m. "I've never seen anything like it before. It's quite extraordinary," an electoral official said.
The Northern Ireland result is expected to be announced in Belfast this afternoon. There is likely to be an immediate dispute over the interpretation of the figures.
Sources in Mr David Trimble's Ulster Unionist Party were claiming last night that a Yes vote of more than 67 per cent would mean a majority of the Protestant and mainly pro-Union community had voted for the agreement.
However, the Democratic Unionist Party has already said that a No vote of 26 per cent or higher would mean a majority of unionists were opposing the agreement.
Today is also likely to see the first shots in the campaign for seats in the Northern Ireland assembly as parties seek to turn the referendum result to their advantage.
The two communities in the North were said to be turning out in approximately equal proportion for the referendum. Unionist areas traditionally characterised by a low turnout were said to be enthused by the campaign and keen to register their ballot.
Different sources said members of the Royal Ulster Constabulary were voting Yes in the majority of cases. The 13,000-strong force with its wide network of family connections will have a key role in shaping the referendum outcome.
The UK Unionist leader, Mr Robert McCartney, said: "There are going to be some surprises tomorrow. I think the No vote is going to be much higher than the government is predicting. It should be at least 40 per cent."
The Queen's University political scientist, Dr Sydney Elliott, predicted a high overall turnout which could contribute to a strong Yes vote of 75 per cent or more.
"I think the Yes campaign turned the corner a couple of days ago. I would expect a result showing 3:1 in favour of the agreement," he said.
Loyalist spokesmen said support for the agreement was as high as 70 per cent in some of their areas. "I feel very confident," said Mr Gary McMichael, of the Ulster Democratic Party, political wing of the paramilitary UDA.
The Alliance Party leader, Lord Alderdice, said he was "very upbeat". Ms Monica McWilliams, of the Women's Coalition, said: "I would be pleased if the Yes vote is in the high 60s."
The UUP deputy leader, Mr John Taylor, said: "I think we are on a roll. I am now hopeful we will get more than a 65 per cent vote." However, the dissident Ulster Unionist MP, Mr William Thompson, said the mood was definitely anti-agreement.
In Dublin political leaders are expecting an overwhelming Yes vote for the Belfast Agreement when ballot boxes are opened.
Party strategists, unusually, declined to speculate on the turnout in either referendum at the close of polls at 10 p.m. because the polling stations were not manned by party activists.
