Even before he touches down at Aldergrove airport this morning President Clinton's visit to Ireland has had a dramatic effect. We have been told - and there is no reason to doubt the reports - that the momentous events of recent days are the result of a great deal of "political choreography" by the US administration, in co-operation with the British and Irish governments.
Gerry Adams's statement that the violence of the past 30 years "must be for all of us now a thing of the past, over, done with and gone"; the announcement that David Trimble has invited the Sinn Fein leader to a round table meeting at Stormont on Monday; judicious leaks that Martin McGuinness is to work with Gen John de Chastelain's body on decommissioning: taken together these constitute the most important developments in the peace process since the referendums in May.
We are a long way from Van Morrison singing Days like This and the euphoria of President Clinton's first visit to Ireland in 1995. We have become more cautious about expressing our hopes for fear of tempting fate. But we have also learned that the political process of creating a peaceful society in the North rarely happens as expected. No side gets quite what it wants when it wants it, or in the words demanded.
There has, inevitably, been criticism that Gerry Adams has failed to utter the phrase "the war is over". But most politicians, including David Trimble, recognise that the Sinn Fein leader has gone as far as can be expected, given the tensions that still exist within militant republicanism.
In the same way, we are unlikely to get the desired handshake between David Trimble and Gerry Adams, much as the White House would probably like it. But there will be a meeting on Monday and if Seamus Mallon has to do most of the talking, so be it.
All this is more remarkable, given the events of the summer, Drumcree and the tragedy of Omagh. The fact that these have drawn politicians closer in implementing the Good Friday agreement is due to a more realistic understanding by all sides of the problems involved. This has come about only with the passage of time. We have all needed space to learn.
In this process, the support of the President of the United States has been crucial. There has been a great deal of criticism of Bill Clinton's visit this time around. He arrives on these shores badly wounded politically, both by the Monica Lewinsky affair and by the bombings in Sudan and Afghanistan.
Comparisons have been drawn between the attack on Omagh and the US bombing of a pharmaceutical plant in Sudan, and Mr Clinton has been accused of "utter hypocrisy" for the decision to visit the Co Tyrone town.
I share the sense of disappointment and bewilderment which most thinking people feel about these issues and understand the indignation felt by those who will take part in protests against US foreign policy.
But I also believe there are very many people alive in Ireland, and further afield, today who would be dead were it not for President Clinton's commitment to the search for peace in Northern Ireland. At the very least, it would have taken a great deal longer to move the IRA to the point of calling a ceasefire and the whole process would have been at even greater risk of breaking down.
The point is worth making because in recent weeks, as President Clinton's reputation has become increasingly tarnished, there has been a tendency to write down his contribution. It's been put to me that, surely, much of what has happened in terms of Washington's involvement in the search for peace was due to the clout of Irish-American politicians, or the influence of certain key advisers in the White House.
Nobody would seek to minimise the part played by Senator Edward Kennedy, Tom Foley, Daniel Moynihan, Bruce Morrison and many others. John Hume's years of work in building a whole network of support in the US predates his dialogue with Gerry Adams and was central to the republican movement's decision to move away from violence and into politics.
But the realpolitik of the situation is that it was only with the arrival of a president who was prepared to become actively engaged that the breakthrough became possible.
We can all recall the critical decisions taken by President Clinton in those early days - the visa for Gerry Adams, the huge political boost given to the Sinn Fein leader, the even more controversial decision to allow Joe Cahill to visit the United States to steady the nerves of militant republican supporters. These were taken against the advice of more conservative officials in the State Department and flew in the face of long-established US policy. President Clinton's sometimes reckless choices and/or his personal pressure persuaded other powerful figures to become involved in the often frustrating search for peace, most notably Senator George Mitchell. We do not know how much influence Mr Clinton brought to bear on Tony Blair but, at the very least, his constant encouragement to the British Prime Minister to stick with the peace process must have helped him and others through some very dark patches.
And then there was the open door policy at the White House, the chivvying and cajoling of politicians and former paramilitaries, many of them taking their first, faltering steps towards dialogue.
Yesterday, in this newspaper, Seamus Mallon laid out an inspiring blueprint of the possibilities for the future, of creating a society in Northern Ireland where people would at last be able "to shed the millstone of a bloody, divisive history and together walk down the road towards a new way of life, with a new vision and above all the confidence to hope".
The final words of this sentence are perhaps the most important. From the very beginning of the long march away from violence and towards peace the most difficult task has been to keep hope alive. On so many occasions, particularly, the obstacles have seemed insurmountable. It was in these bleak hours that the determined optimism of the most powerful political leader in the world, his belief that the peace process could work were, literally, irreplaceable. We have now reached a point where the road ahead seems somewhat less frightening and the politicians more sure-footed. Miraculously, the terrible events of the summer, which in the past would have certainly driven both sides further apart, seem to have brought people closer together in their determination not to lose the peace. It may be that we are close to being able to manage on our own. But this has been a momentous week in the process of securing peace and it is fitting to express our gratitude to the American President who has done so much to help us achieve it.