A rejection of the constitution by French and Dutch voters next week could lead to a massive loss of political momentum, writes Denis Staunton in Brussels.
As Europe awaits next week's referendums on the EU constitution, yesterday's front-page headline in Le Monde captured neatly the anxiety felt in the continent's capitals.
"Allemagne, France, Pays-Bas: l'Europe hésite sur son avenir" (Germany, France, the Netherlands: Europe frets over its future).
With the French and the Dutch looking ever more likely to vote No and Germany facing into a sudden election campaign, the EU is on the verge of a crisis that could halt both the expansion and the integration of Europe for years.
In public, EU leaders and the European Commission say that two No votes next week will not stop the process of ratifying the constitution and that Ireland, Britain, Denmark and others will hold referendums as planned. Privately, most senior politicians and their officials admit that the constitution is unlikely to recover from rejection by two of the EU's six founding member states within a single week.
The Taoiseach insists that Ireland's referendum will go ahead regardless, but senior Government figures acknowledge in private that a No vote in even one country would make winning a referendum in Ireland a lot more difficult.
The EU constitution says that if at least four-fifths of the member states ratify it and the rest do not, EU leaders are to meet to discuss the situation and decide what to do. If only small countries, new member states or the semidetached, such as Britain and Denmark, reject it, the constitution would probably be adopted by the others.
But if France says No, it is all but impossible to foresee the constitution coming into force in its present form.
Some No campaigners in France believe the constitution could be renegotiated, improved and presented for approval a second time. This is true in theory. However, the negotiations that led to the text agreed by 25 leaders under Ireland's EU presidency last year were so lengthy and difficult that any renegotiation is also likely to be prolonged, and a more successful outcome is not guaranteed.
If the EU has to abandon the constitution, it must carry on initially under the provisions of the Nice Treaty, perhaps with a few adjustments that do not require formal treaty change. As Sebastian Kurpas points out in a new policy brief for the Centre for European Policy Studies, a Brussels think tank, EU leaders could agree unanimously to make some changes, such as appointing an EU foreign minister and creating an EU external action service, or diplomatic corps.
Other changes, such as new voting arrangements in the Council of Ministers, where national governments meet, or the abolition of national vetoes, would require referendums in some countries, including Ireland.
Such institutional changes are not, however, the most important difference the constitution would make to the EU. Its main innovation is that it creates the basis for dynamic change, so that the EU can adapt more easily to new circumstances and can deepen integration at the pace chosen by its member states.
Giving up on the constitution would mean a massive loss of political momentum, leaving the EU, as one senior European diplomat put it yesterday, "like a balloon that has been deflated - it just lies there and looks ugly".
The EU has traditionally drawn strength from crises, turning them into an opportunity for further political integration. No such initiative is likely this time, not least because of the unprecedented leadership vacuum at the top of European politics.
The biggest four member states - Germany, France, Britain and Italy - are governed by wounded leaders, all of them probably serving out their final months in office. To make matters worse, the commission, which is charged with defending the interests of the EU as a whole, is under the calamitous command of José Manuel Barroso, whose clumsy handling of every political decision that has come his way has left him liked by few, trusted by fewer and respected by none.
Europe may be about to enter a period of "Eurosclerosis" such as that which settled on the continent during the 1980s when member states looked inward and Brussels was almost forgotten. Without its constitution the EU will continue to function: leading trade negotiations, regulating competition between companies and enforcing common rules agreed by the member states.
The union will probably accept some new member states - Bulgaria, Romania and perhaps Croatia - although Turkey may have to wait another generation. But the EU's ambitions to play a bigger role on the world stage and to enjoy a more equal partnership with the United States will be more difficult to realise than ever.
This stagnation will do nothing to endear the EU to its citizens or to overcome the sense of alienation some Europeans feel towards Brussels.
A weak, directionless EU would be poorly placed to offer either the "added value" promised by policymakers or a sense of common citizenship that could form the basis of a more democratic Europe.