When one recalls how close he came to political oblivion - as the polls dipped badly in the last week of the referendum campaign - David Trimble can afford to be surprisingly relaxed this week.

The legislation announced by the government on prisoners did not contain any unpleasant surprises for him. Perhaps even more remarkably the policing issue - quite conceivably the most explosive - seems to have been resolved for the time being by the appointment of the Patten Commission.

But Mr Trimble is not out of the woods yet. There is still an uncertain election campaign to fight.

His opponents in the Democratic Unionist Party have responded smartly to their referendum defeat and shifted their ground in subtle ways. Knowing full well that the DUP has the vote anyway of those who want to see an anti-Agreement wrecking policy in the Assembly, the DUP now presents itself in a more moderate light.

The DUP's brilliant party political broadcast last week presented a new DUP: significantly only allusive reference was made to Dr Paisley.

This new DUP was a party of the respectable middle class alarmed by the prospects for investment if terrorists entered government; a party of mothers worried about the public morality of releasing paramilitary prisoners; a party, in other words, which shared concerns which are widespread within the Protestant community.

The DUP's new stance is to acknowledge, as `democrats', the outcome of the referendum, but to present themselves as the guarantors of the Trimble/Blair pledges on paramilitary violence and cross-border bodies which accompanied the Agreement - pledges which they claim cannot be honoured because they conflict with the Agreement.

`Vote DUP - it's your only guarantee' goes the slogan - if you want to see the Trimble/Blair themes of reassurance implemented and the vast majority do so wish.

It is a smart move. The logic is that the DUP (to the disappointment perhaps of Alliance ministerial hopes) should take up ministerial positions to test realities on the cross-border issues.

There is only one way for the Ulster Unionist Party to deal with the modernised DUP stance: it is to take the high ground of the Agreement. It is frequently said that the No side fought a brilliant referendum campaign - only to be blown off course by Tony Blair's last-minute interventions.

The Prime Minister managed to convey a powerful subliminal message. The union based on consent is secure - as the Agreement explicitly states; the sovereignty of Westminster remains.

But the union is not just a cold institutional legal reality. It is also an emotional relationship involving the people of the rest of the United Kingdom and Northern Ireland. They have many historical ties.

The more tolerant Northern Ireland which the Agreement attempts to promote would also be a Northern Ireland which had a more relaxed and widely-admired status in the UK.

Mr Trimble has now become the symbol of the possibility of this new relationship. As such he is indispensable to any form of unionist politics which recognises that Tony Blair is likely to be Prime Minister for at least 10 years.

There is no denying the importance of Mr Blair's intervention. But the fact remains that the No constituency in unionism has not produced that quality response to the Belfast Agreement which marked, say, the unionist reaction (in pamphlets, speeches, newspaper articles and eventually books) to the Anglo-Irish Agreement.

This is the obvious weakness at the heart of the No case. In a recent article in Parliamentary Brief Sir Kenneth Bloomfield - the former head of the Northern Ireland civil service - has given us an important clue as to why: there is in reality a huge difference between the unilateralism of the 1985 Agreement and the mutuality of the 1998 one.

The democratic inclusiveness of the new Agreement - combined, of course, with what Sir Kenneth calls the `immense difference' in the way nationalism now treats the status of Northern Ireland - makes it much harder to attack.

Nevertheless, there are still important unresolved problems. The Trimble-Ahern deal that is the Belfast Agreement is in reality the deal promoted by John Taylor and John Bruton in 1995. If anyone doubts this, they should study again John Taylor's Irish Association speech of that year, with its prediction of a rainbow coalition plus sensible cross-borderism underpinned by the removal of Articles 2 and 3, and they should compare it with John Bruton's contributions to the Forum for Peace and Reconciliation.

The then Taoiseach argued that Article 2 and not just Article 3 of the Constitution had to be revised. He also made it clear that he insisted only on practical cross-border co-operation.

But neither Mr Taylor nor Mr Bruton could deliver enough people within unionism or nationalism for such an accommodation. In 1998 Mr Ahern and Mr Trimble, who shied away from such a deal in 1995, proved that they could deliver it.

Since then some of Mr Trimble's own Ulster Unionist supporters claim to feel betrayed.

This is understandable in a way, but his critics now have a hard choice. Ulster Unionism has finally produced a leader who commands genuine respect in Downing Street: how can he possibly be challenged by those who have, at best, less than distinguished reputations on the other side of the water?

But Mr Trimble's project is partly dependent on developments within nationalism. The mood within Sinn Fein is unusually hard to read.

It veers from apparently self-confident, "in the know" pronouncements about the strategy of both governments to a rather self-contradictory, nervous maximalism on the policing issue.

In recent polls, however, Sinn Fein has tended to lag behind the SDLP. If Northern Ireland really is moving away from a political culture based above all on a sense of historic grievance, this certainly appears to pose more problems for Sinn Fein than for the SDLP.

The SDLP has a policy culture of sorts; Mark Durkan, for one, has thought deeply about the modalities of the good government of Northern Ireland and is itching to get his chance. Is there really an equivalent within Sinn Fein?

The Agreement fulfils the historic objective of the SDLP, but it certainly does not do the same for the Republican movement.

Mr Adams frequently gives the impression that the war is over. But as yet he has refused to say so explicitly - even though it would hasten a genuine engagement with unionists.

Some republicans still give the impression that they hope the appearance of an adherence on their part to the TUAS (Tactical Use of Armed Struggle) strategy might yet provoke a major split within unionism. It is indeed still a possibility.

But so far Mr Trimble has kept one step ahead of the game. If he continues to do so, the only alternative for republicans will be to make the best of the Agreement.

Paul Bew is Professor of Irish Politics at Queen's University, Belfast.