According to opinion polls,more than half of Protestants are against the agreement and intend to vote "No" in Friday's crucial referendums. The votes, which were supposed to cement the agreement as the instrument which will mark the end of the Troubles, may instead turn out to be a device for institutionalising stalemate.
There is, in other words, an emergency in the peace process, and one which will next week bring Tony Blair to Belfast for the third time in an effort to change Unionist minds. The Prime Minister has to hope that either the polls are wrong or that a last-minute change of heart will sweep through Unionism.
The problem is that while practically all Catholics and nationalists, north and south, favour the accord, a Protestant majority is, according to the polls, building against it. If that majority is confirmed in the vote, the whole deal could be undermined.
The Government's nightmare scenario runs like this. Nearly all the Catholics, together with the smallish centre-ground and a minority of Protestants, vote for the agreement, producing a vote of say 60-40 in its favour. On the straight arithmetic the agreement has thus won popular endorsement; but politically it has been hobbled, for it is evident that a majority of Unionists have voted against it. This will immediately weaken the position of David Trimble as Ulster Unionist leader.
A vulnerable agreement and a vulnerable Mr Trimble will then face assembly elections scheduled for 25 June. These will be preceded by an intense struggle for control of the Unionist party, since the "No" camp will seek to nominate anti-deal candidates.
Then, on 5 July, coming up in Mr Trimble's Upper Bann constituency is Drumcree, the annual Orange marching confrontation which the "No" camp will seek to turn into a festival of opposition to the agreement.
The next nightmare for Mr Blair, Mr Trimble and other pro-agreement elements is that the Rev Ian Paisley, his ally Robert McCartney and anti-agreement Unionists will together control more than half the Unionist members of the assembly. Under the intricate rules laid down in the agreement this would be enough to allow Mr Paisley to impose gridlock. Even if he does not take more than half the Unionist seats, a strong showing on his part will undoubtedly give rise to bitter procedural trench warfare in the assembly.
This possibility has come into closer focus as the opinion polls have pointed to a steady growth in the percentage of Protestants preparing to cast a "No" vote. A pro-agreement loyalist said yesterday: "I think there was a complacency in our campaign which shouldn't have been allowed to develop. The `No' campaign has been organising for six months."
A Government source said: "The Unionist party were slow in starting and their campaign has not been very well co-ordinated or effective. It's looking awful - we're losing votes by the day. It's really bad news."
The polls and anecdotal evidence indicate that a number of issues trouble Unionists. They are afraid that Gerry Adams will be able to walk into government without the IRA de-commissioning a single gun, and they worry about the future of the union with Britain.
Most of all, they say, they disapprove of the early release of paramilitary prisoners - epitomised when members of the Balcombe Street gang, who killed 16 people in England in the 1970s, were greeted rapturously at last weekend's Sinn Fein ard fheis (conference), an act seen byUnionists as sheer triumphalism.
But a Catholic lawyer snorted: "This stuff about prisoners is all camouflage. The real objection is that they [Protestants] can't stomach the idea of doing a deal with nationalists, Catholics, treating them on equal terms."
A loyalist source denied this interpretation. "The major issue is the notion of Sinn Fein in government, closely followed by the prisoners. But there's also a paranoiac lack of self-confidence in Unionism about what their opponents say - they think if Gerry Adams likes it then it must be bad for them."
There are so many radical new departures in the agreement that Mr Paisley has been given great scope to cherry-pick ammunition for his "No" campaign. The "Yes" campaign's strongest counter-argument is that the nay-sayers offer no alternative in place of the agreement: that argument has however yet to bite.
The "Yes" campaign set out with the hope that the voters would be swayed by the argument that the referendum choice was between the past and the future, between sentencing Northern Ireland to perpetual conflict or making a historic fresh start. The powerful simplicity of that concept has become muddied in the last few weeks.
A "Yes" campaigner said yesterday: "Paisley and McCartney are pressing all the fear buttons. People don't seem to realise that a `No' vote would be catastrophic and would result in the world turning its back on us."
The "Yes" people thus go into the final week of the referendum campaign hoping that another Blair visit will help turn the tide.
Focus, page 25