French supporters and opponents of the new EU constitution have held final rallies ahead of Sunday's vote.
Friday's gatherings were the last chance to rally support
German and Spanish leaders threw their weight behind the "Yes" campaign in two Socialist Party gatherings.
But leading Socialist dissenters joined with Communists and union leaders in Paris to urge a "No" vote.
Germany's parliament completed the ratification of the charter on Friday, with an upper house vote designed to boost France's struggling "Yes" camp.
Latest opinion polls have provided mixed messages, one suggesting support for the "No" campaign had fallen to 52%, another that it was up to 56%.
Campaigning ended at midnight local time (2200 GMT) on Friday before the Sunday referendum.
Both the governing centre-right UMP party and the opposition Socialists urged voters to support the proposed constitution.
On Friday evening, Socialist party chief Francois Hollande welcomed Spanish Prime Minister Jose Luis Rodriguez Zapatero at a rally in the northern city of Lille.
"Europe needs France, its enthusiasm, its culture, its strength and its momentum," he told a crowd of about 3,000 people, adding that the "No" campaign was "sad and pessimistic".
At a smaller gathering in the southern city of Toulouse, German Chancellor Gerhard Schroeder asked the French to vote "Yes" with their hearts and their heads.
Several hundred people gathered for a "No" rally in Paris, organised by various left-wing parties and trade unions.
The "No" camp is confident of victory
The BBC's Sarah Shenker at the rally says the "No" campaigners are already contemplating how to use the political capital they might gain from victory.
Socialist dissenter Henri Emmanuelli denied that the campaign was negative.
"'No' is not the end of something, it's the beginning of something, it's the beginning of a great hope," he told the crowd.
Far-right National Front leader Jean-Marie le Pen, who also backs the "No" campaign, addressed a public meeting in the south-eastern town of Villeneuve-Loubet.
On Thursday President Jacques Chirac went on TV to call for a "Yes" vote, which he said was vital for the future of both France and Europe.
And one of the main architects of the constitution - former French President Valery Giscard d'Estaing - made an emotional appeal to the people of France in a speech to the German parliament just before its vote on Friday.
The campaign has been overshadowed by a gloomy mood brought on by years of faltering growth and unemployment of around 10%.
Treaty rejectionists are also ahead in the Netherlands, which will hold its referendum on Wednesday.
The EU constitution has to be ratified by all 25 member states to become law.
France is the second EU member to hold a referendum on the document. Spain's referendum resulted in a "Yes" vote, which was then ratified by both houses of parliament.
The treaty aims to streamline decision-making in the enlarged EU of 25 nations.