Zero-Sum politics, where one party can only win at the expense of another, is threatening the latest effort to provide a balanced political settlement in Northern Ireland.
The united front of Dail parties in favour of the Belfast Agreement has persuaded voters in the South this settlement is worth supporting, even though it proposes to alter Articles 2 and 3 of the Constitution; guarantees there can be no change in the status of Northern Ireland without the consent of a majority of the population there; and replaces the Anglo-Irish Agreement.
But the positive reception the agreement has received in the South - and among nationalists in the North - has fed unionist fears and provided ammunition for an effective "Vote No" campaign by the DUP and the UKUP.
From a situation where, in the euphoria immediately following the agreement, the population of the Republic was less supportive of the political settlement than citizens in the North, the position has been reversed.
The declared No vote in the South has been cut from 20 per cent to 5 per cent in four weeks, while the percentage in favour has risen from 61 to 72 per cent.
At the same time, the undecided vote has climbed slightly from 19 to 23 per cent.
The change in Southern public opinion reflects the "selling process" engaged in by Fianna Fail and the opposition parties, together with Sinn Fein's unambiguous endorsement of the document and that party's intention to take seats in the Northern Ireland assembly.
Opposition to the agreement dropped precipitously within all parties, but it was particularly marked within Fianna Fail and Fine Gael where it has fallen from 21, to 3 and 4 per cent, over the past four weeks.
Within the Labour Party, the drop was from 18 to 8 per cent. But the Progressive Democrats bucked the trend - almost certainly over prisoner release - and support for the agreement within that party fell, from 81 to 55 per cent.
While the electorate was taking its lead from the political parties, there was little evidence of increasing expectations that the settlement terms would bring peace.
Last month, chances of securing lasting peace was given at 55 per cent by the Southern electorate and this has increased marginally to 57 per cent.
The section of the electorate that rates the changes of lasting peace as poor, or very poor, has dropped from 18 to 17 per cent.
Evidence of Government confidence that the referendum will now be overwhelmingly carried in this State - and that Sinn Fein and the IRA are firmly wedded to the process - came yesterday when the Taoiseach, Mr Ahern, turned his attention to Northern Ireland and addressed unionist concerns.
He assured them the agreement would require a commitment by all parties to non-violence and to exclusively peaceful and democratic means.
And, following his call for the IRA to declare its war was over, Mr Ahern insisted republican and loyalist paramilitaries would have to address arms decommissioning next June, after the agreement was endorsed. They would have to co-operate with the International Decommissioning Body, he said. Otherwise, there would be "no way forward" for those parties.
The British Prime Minister, Mr Tony Blair, delivered a somewhat similar message in Belfast, as he sought to reassure unionists and to sway the high level of undecided voters towards a Yes vote.
He promised to give legislative expression to the need for arms decommissioning and for the use of exclusively peaceful and democratic means. And he pledged there was no question of disbanding the RUC or creating a situation where paramilitaries took over local policing.
The governments' move to shore up falling unionist support for the agreement comes a week before polling day. The findings of the Harris survey conducted as part of an Irish Times/MRBI opinion poll, show support for the agreement has dropped by 15 points in the past month to 69 per cent in Northern Ireland, while the percentage opposed has grown from 16 to 31 per cent.
Should the governments fail to reverse that trend, there is the prospect that a majority of unionists could vote against the agreement on May 22nd.
By contrast, support for the agreement stands at 94 per cent among nationalists in Northern Ireland, with 6 per cent undecided.
The positive reaction by SDLP and Sinn Fein voters has, inevitably fed unionist concerns and fears. And it has activated a zerosum politics response.
The task facing both governments and moderate civic leaders is to convince the electorate that both communities can win by endorsing this agreement.