If Peter Mandelson is kidding himself, he's fooling no one else. As David Trimble confronts political mortality, Mr Mandelson assures us the Belfast Agreement is secure.

Nodding to the democratic imperative, the Northern Secretary informs the unionist rejectionists that the government is listening to their concerns. In the next breath, he intimates they will be ignored: a "minority" cannot be allowed to veto the political process.

Anti-agreement unionists might snarl that London and Dublin are not so quick to apply that principle to the minority party of the nation alist/republican community in Northern Ireland. They will at any rate conclude that Mr Mandelson's grasp of simple arithmetic is as tenuous as his hold on political reality. Minority? Secure?

The BBC's distinguished Ireland correspondent, Denis Murray, informed us on Saturday night that the agreement had never been in greater trouble. He may have based that sound judgment on a conspicuous fact which the government wishfully ignores: the democratic, cross-community basis on which the agreement relies has imploded.

The Rev Martin Smyth's 43 per cent of the Ulster Unionist Council, plus Dr Paisley's DUP, Mr Robert McCartney and other smaller groupings constitute a clear pro-Union majority against the agreement, at least as things now stand.

The numbers in the assembly may sustain the theory of a working majority for the implementation of the agreement. However, the legitimacy of that mandate is increasingly challenged by the certainty that elections held now would produce a very different result.

Moreover, even if Mr Trimble hangs on (and his inclination will be to do so while he has a majority of just one), it is now clear that his party will hold him to the terms of the manifesto on which he fought the last assembly election.

Mr Mandelson may dislike the trade-off between guns and government, thinking it counter-productive and a probable guarantor of neither, but the "Mexican standoff" within Ulster Unionism now seems set in stone.

It was surprising, by the by, that Mr Trimble did not protest vigorously at Mr Mandelson's recent re writing of the history of last Nov ember. The proposed trade-off did, however briefly, deliver devolved government, he might have argued.

Some of those close to him were also intrigued that he declined to accuse publicly the Taoiseach and Seamus Mallon of bad faith in seeking to prevent, and subsequently to overturn, the suspension of the executive - with the clear (if unsustainable) implication that Mr Mandelson should have been prepared to lose him, if need be, to preserve the agreement.

Whatever the reason for his diplomatic silence then, no matter now, and whatever hopes were fanned by his St Patrick's Day pronouncements in Washington, they were surely extinguished on Saturday afternoon.

Mr Trimble insists that, if anything, he tightened his position on decommissioning on March 17th, but if he was misrepresented by the media, he was also badly misunderstood by other key players in the peace process.

London may have been more cautious but Dublin certainly believed the Ulster Unionist leader had signalled something of significance. He appeared to do so again last Thursday in his interview with The Irish Times.

In the Department of Foreign Affairs and the Office of the Taoiseach, close textual analysis would have homed in on his insistence that he would not be "prescriptive" in his approach to decommissioning; on his reluctance to get into the detail of the how and when; and his failure to dispel wholly the thought that he might be tempted by some new republican assurances which were less than time-specific.

In fairness to Mr Trimble, that British caution was wholly justified. In Washington he undoubtedly gave legs to the Irish quest for an "alternative context" in which the arms issue might be addressed.

Irish hopes were further raised by the patent anxiety of some of those closest to Mr Trimble to find a way off the decommissioning hook.

However, as for Mr Trimble himself: the sum total of his Washington remarks and subsequent elaborations, taken together with the realities of his domestic political situation, left little doubt that those "legs" would inevitably lead him back to decommissioning.

Had he won handsomely on Saturday, the political environment might have been transformed, at least for a short time. New opportunities might have arisen, for there are consequences from the renewal of any leader's mandate.

Michael McGimpsey is apparently satisfied that Mr Trim ble's mandate has been refreshed, his "working" majority sufficient unto the day. Few objective observers would agree with him. Loyalty to the leader is all very well; however, the pretorian guard in any party is of little use to the leader if it is blind to the political realities.

The reality is that the Trimbleistas are heading for defeat. If that is the end result, moreover, they will themselves have contributed heavily to it. The political misjudgment which had some of them gleefully welcome Mr Smyth's leadership challenge certainly speaks for itself.

Content to characterise him as "yesterday's man", an ageing dinosaur, some of Mr Trimble's strongest supporters convinced themselves Mr Smyth would poll a maximum vote of 30 per cent. Well, the dinosaur - at two days' notice and with no campaign - came perilously close to unseating the leader.

Mr Smyth made clear he had no desire for the job. It is an open question whether the presence of a younger, more plausible contender - Jeffrey Donaldson - would have seen Mr Trimble done for on Saturday.

We do know for certain that Mr Smyth gathered the swirling discontents within unionism made more specific in David Burnside's motion on the RUC.

These discontents extend way beyond the narrow issue of decommissioning and the Trimbleistas should have seen the tidal wave co ming. Certainly they were warned, as recently as last week by one of their own number, Dermot Nesbitt.

At Monday's meeting of the UUP assembly party, Mr Nesbitt reportedly disagreed with Sir Reg Empey, warning Mr Trimble that their problem lay not just with the always-anti-agreement faction but with previous supporters who had grown disillusioned with the entire direction of the political process.

That disillusion is now manifest. Having apparently failed to detect it, Mr Trimble shows signs now of having heard it. On Saturday afternoon, with the sounds of internecine strife all around him, he acknowledged the warning and promptly redirected it to the appropriate place. This was a mighty warning to both governments. David Trimble's room for manoeuvre has been closed off. If the agreement is to be saved, it is the republicans this time who must jump, and quickly.