Northern Ireland politics is not for the fainthearted. There is never a dull moment and the thrills and spills of the referendum campaign will continue until the votes are counted.
When the last opinion poll commissioned on this issue by The Irish Times was published on April 16th, it was apparent, even amid the euphoria generated by the events of Good Friday, that Northern unionists were less enthusiastic than their nationalist neighbours.
At that time, with five weeks to polling day, there was 90 per cent support for the deal among Catholic and mainly nationalist respondents but a more muted 62 per cent support in the Protestant and mainly unionist community. Among supporters of the Ulster Unionist Party, 70 per cent declared their intention at that time of casting a Yes vote in the referendum.
As expected, the Catholic vote in Northern Ireland has held up, with the latest poll showing 87 per cent support for the agreement. But there has been a substantial decline in Protestant support for a Yes vote, to 36 per cent.
The No vote among Protestants has risen from 22 per cent following Good Friday to 40 per cent when fieldwork for the latest poll was conducted last Tuesday and Wednesday. The proportion of Protestant "don't knows" has risen from 16 to 24 per cent.
Among UUP supporters, the Yes vote has fallen 18 points to 52 per cent; the No vote has risen slightly, from 16 up to 19 per cent but the "don't know" camp has more than doubled, from 14 to 30 per cent.
As well as sowing the seeds of doubt among mainstream unionists, the Democratic Unionist Party has solidified opposition to the agreement among its own adherents.
Immediately after Good Friday there was a sizeable 30 per cent support for the pact among DUP voters, but the Rev Ian Paisley and Mr Peter Robinson had managed to reduce this to 3 per cent by last Tuesday.
Overall, one could say the DUP has rallied its troops while UUP voters are wavering badly. This reflects the energetic and well-focused drive for a No vote which has been in contrast with a proagreement campaign among unionists that seemed to lack fire.
The reasons for respondents voting against the agreement are revealing. The release of prisoners is the biggest turn-off, cited by 45 per cent of No voters (including 50 per cent of UUP supporters who are voting No).
"The beginning of a move towards a United Ireland" is next, at 18 per cent.
The prisoner release issue was not a direct element in the three strands of the multi-party negotiations, although clearly a major factor in keeping Sinn Fein on board in the closing stages.
Constitutional issues might be somewhat abstract but the sight of an ex-prisoner, who may have killed one of your neighbours, walking the streets of your town or city is calculated to turn the stomach of the average unionist voter.
Senior UUP sources believed the Balcombe Street display at the Sinn Fein Ardfheis had increased the No vote in unionist ranks by about 10 percentage points.
Middle-ground supporters of the agreement in Northern Ireland are at a loss to understand how the gaffe of releasing the prisoners to attend the RDS was possible, given that - apart from the double standards shown regarding the murder of Det Garda McCabe as compared with killings of RUC members - Dublin has by and large been fairly sensitive in its approach to the peace process.
An opinion poll is a snapshot and it is impossible to deduce from these findings whether the slippage of the Yes vote has been arrested, first by the decision of Dr Paisley to pull out of debating with UUP leader Mr David Trimble on television and now by Mr Blair's latest intervention.
Whatever the rights and wrongs of the Northern Ireland Office decision to release the loyalist paramilitary Michael Stone to attend an Ulster Democratic Party rally at the Ulster Hall, the action will have done nothing to reassure middle-ground Protestant opinion, which feels almost as much distaste for convicted loyalist killers as for republican ones.
On the nationalist side, there seems to be little doubt as to the importance of securing passage of the agreement.
No less than 96 per cent of SDLP voters are in favour, with 83 per cent support from the Sinn Fein camp.
Party voting intentions have shifted somewhat since the previous Irish Times/MRBI poll. The UUP scores 23 per cent, compared with 30 in the last poll, with the SDLP on 24 per cent compared with 21 last time. The DUP scores a plausible 14 per cent but there must still be some shy Sinn Fein supporters out there as the latest poll figure of 7 per cent is likely to be well surpassed on polling day.
The overall picture suggests that only a decision by the UUP's Mr Jeffrey Donaldson to change his mind and urge a Yes vote can have any prospect of altering the course of this referendum campaign. Otherwise, we appear to be looking at a narrow victory for the Yes camp, with a majority of unionists voting No.
It's said the darkest hour is just before dawn and, from the point of view of Yes campaigners, the hour could not be much darker.