This will be a contest for the very soul of Unionism

Saturday's vote on his leadership of the Ulster Unionist party could well be a make-or-break moment for David Trimble, strengthening his authority in the party or rendering him a lame-duck leader.

Either way, the result will have huge implications for the entire peace process. For its supporters, the worst-case scenario is that a bad result for Mr Trimble will lead to his departure and replacement by an opponent of the Good Friday Agreement.

Some of his potential successors are dead set against the accord and indeed the peace process in general. Others have an ambivalent attitude towards it, though nearly all of them are much less enthusiastic about it than Mr Trimble has been.

With the possible exception of Ken Maginnis MP, none of Mr Trimble's closest supporters is considered, to use a word not generally used within the party, to be papabile.

The peace process is already considered by all sides to be in deep trouble, but a Trimble exit could prove fatal to the whole exercise. Much is therefore at stake in Saturday's vote. It is hardly an exaggeration to say that it will be a contest for the soul of Unionism, which as a movement has been deeply divided by the peace process.

Although Mr Trimble has been mercurial and unpredictable, there is no question that he sees himself, and is seen, as a moderniser who believes Unionism's basic interests dictate that it has to pitch in and hammer out a negotiated settlement.

The Reverend Martin Smyth, by contrast, represents that substantial section of old-fashioned Unionism which believes that high-level political negotiation is, by and large, a bad idea. This traditionalist view holds that it is better, in a phrase, just to say no.

This camp tends to regard Mr Trimble as having been foolish to enter the political whirlpools which have produced developments such as the Good Friday Agreement, and other elements of which they disapprove. The Trimble camp in return tends to portray the older anti-agreement elements as dinosaurs with a policy akin to that of King Canute.

Mr Smyth himself can hardly expect victory tomorrow. At the age of 68 he is thought to be approaching the end of a long political career during which he headed the Orange Order for 25 years and has been an MP for almost two decades.

When Mr Trimble was elected leader in 1995 Mr Smyth finished last on the slate of five candidates, gaining only 60 of the 800 votes cast. Thus, although he is widely respected by the grassroots, he has never really been regarded as a potential leader.

His ambition is therefore not to become leader but to fatally undermine the Trimble policy. The Ulster Unionist party has been riven with division for so long that yesterday there was some relief in the air that the differences might at last be brought to a head.

The fact that half or more of the general Protestant population opposes the Good Friday Agreement to a greater or lesser degree has proved a major inhibiting factor in the peace process.

The Ulster Unionist Council, which will vote today, is a legendarily volatile and unpredictable body, many of whose members arrive at its meetings undecided and make up their minds only after hearing the speeches.

Some are inclined to think that Mr Trimble is right to persist with the peace process even though they think of it as having many drawbacks. Others long to turn back the clock, and prefer old certainties to uncharted new waters.

In between these two poles the Council contains a large floating vote, torn between modernisation and tradition. The fate of Mr Trimble, and perhaps the overall peace process, may depend on their last-minute decisions on how to cast their votes.