Three countries have already said "yes" to the EU constitution. On Sunday, Spain becomes the first country to put the matter directly to the people. Here's a look at the remaining hurdles for the constitution.
Spanish Premier Zapatero has it easier than most EU leaders
Amid fears of an embarrassingly low turnout Spaniards began voting Sunday in a referendum on the proposed EU constitution which most of the 35-million electorate
profess to back. "Today we are taking a decision of great importance for the future of a united Europe, and also for Spain, for its future and its well-being," Spanish Prime Minister Jose Luis Rodriguez Zapatero said as he cast his vote Sunday.
Spain is the first of 10 EU member states holding a popular vote on the text which is designed to streamline decision-making in the 25-member bloc which last year took in 10 new, mainly Eastern European, members.
Opinion polls have consistently shown the "yes" camp well ahead of those opposed, with some 45 percent of voters asked saying they back the constitution to only seven or eight percent defiantly against.
The Spaniards have kicked off a long ratification process.
At the EU Summit in Brussels last June, the UK Independence Party poster placed a poster in Brussels asking the United Kingdom's Prime Minister, Tony Blair, not to sign the European Constitution
So far, Lithuania, Hungary and Slovenia have already given the constitution the green light via their parliaments, but Spain's referendum is the first of 10 polls. With voters from euroskeptical countries like Denmark, Britain, Ireland and France still in line, the EU constitution's fathers and mothers will be waiting uneasily in the months to come. Only one country needs to reject the document for it to fail.
Spain's approval looks certain but is by no means guaranteed. The latest survey showed 51.2 percent of Spaniards in favor but the poll had a margin of error of 2 percent, so everything is still open in the country on the Iberian peninsula.
French go to polls in the summer
French President Jacques Chirac is an advocate of the EU constitution. But he has some work ahead to convince his countrymen and women who could go to the polls in June. An early February poll by the Ifop polling company put the proponents ahead of the opponents 25 to 20 percent with a large 46 percent undecided. In 1992, the French made the EU nervous when they narrowly approved the Treaty of Maastricht, which among other things created the foundation for the EU's common currency, the euro.
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London will be taking its time, waiting until early 2006 before letting Brits go to the polls to decide. The Danes have already rejected two EU treaties in 1992 and 2000. The political leaders in both the government and the opposition don't want to see that happen in this vote and are asking their supporters to vote "yes." The Irish, another nay-sayer to an EU treaty, are leaning towards approval.
Finally, the outcome of the referendum in Poland is unclear because of a lack of interest. In order to ensure the 50 percent voter participation required to make a referendum valid, the government will combine it with national elections.
Not all EU citizens get to vote on their constitution
The EU's most populous country, Germany, is not putting the matter to the people. Both houses of parliament must ratify the treaty with a two-thirds majority. This Friday, the upper house, the Bundesrat, began the ratification debate. In less than one week, the lower house, the Bundestag will have the topic on the agenda. The country's two largest parties, the ruling Social Democrats and the conservative Christian Democrats, both favor the constitution.
Foreign Minister Joschka Fischer has said he wants the ratification process over before parliament's summer break.
All eyes on Europe
By October 2006, all 25 countries, in whichever way they feel is appropriate, must have approved the constitution. If one bad apple spoils the bunch and a country rejects the constitution, the document would have to be reworked. Or the country would have to renegotiate its status with the EU.
If all countries approve the document, it will become binding in 2007, introducing new EU posts such as an EU foreign minister and an EU president, who would sit at the head of the board of European leaders.