Now, as the Netherlands appeared set Wednesday to reject the charter, too, the 25 EU governments may finally be forced to outline a blueprint for the future.
EU leaders intensified negotiations to salvage the treaty as the Dutch voted on the constitution 72 hours after the French 'no.' Opinion polls indicated about 60 percent opposition in Holland, even higher than the 55 percent in France.
So far, the EU has refused to discuss a Plan B, fearing that would embolden naysayers. Observers say alternatives might include a redrafting of the treaty, a drive to make France and Holland vote again, or even a Europe-wide referendum on a single day.
On Wednesday, EU leaders showed signs of scrambling to devise a game plan, which would likely be formally unveiled at a June 16-17 European summit.
In Brussels, European Commission President Jose Manuel Barroso discussed the fate of the constitution with his 25-member EU executive, which backed his view that the treaty is not dead but that its ratification must continue in all EU member nations.
"It is up to the member states to decide what to do now," said EU spokeswoman Francoise Le Bail.
Luxembourg Premier Jean-Claude Juncker, whose nation holds the rotating EU presidency, held one-on-one meetings with his counterparts from Slovakia, Portugal and Austria at a Luxembourg chateau where he will meet all EU leaders before he chairs the upcoming European summit.
The way ahead looks very fuzzy.
Austrian Chancellor Wolfgang Schuessel's proposal this week for an EU-wide referendum has already been rejected once. A panel of 105 representatives of EU governments, legislators and the European Parliament that wrote the constitution found the idea legally unfeasible.
One possible avenue for saving the treaty is a clause that says EU leaders will discuss what to do if, by October 2006, four-fifths of member states have ratified the treaty but one or more others have "encountered difficulties" getting it accepted. Those countries might theoretically be asked to vote again.
There would be precedents for a revote in France or the Netherlands — past EU treaties have triggered repeat referendums in Ireland and Denmark.
In the latter two, however, a revote sorted out unclear texts on specific issues such as immigration and defense. The French and the Dutch harbor an across-the-board dissatisfaction with across-the-board European integration that is hard to fix with a few tweaks.
"You cannot proceed without France," said Daniel Keohane, a senior research fellow at the London-based Center for European Reform. "If (Euroskeptic) Britain voted no, you could argue it is more Britain's problem than Europe's."
In a pinch, the EU can stick with the current EU statutes.
The Treaty of Nice, however, is widely seen as a shoddy piece of work, patched together at a raucous five-day summit in December, 2001. For instance, it grants Poland, with 8 percent of the EU population, 27 votes in decision-making ministerial meetings — two fewer than Germany, which has 20 percent of the bloc's population.
It was, in fact, that treaty's shortcomings, especially its shake vote-allocating, that triggered the constitution negotiations.
Not everyone is convinced the treaty can be salvaged. The EU charter is dead, according to Neil Kinnock, a former EU commissioner. "I have no doubt at all about that," he said this week after the French referendum result was announced. "Referendums produce results and results have got to be lived with."