French President Jacques Chirac has made a televised appeal to sceptical voters not to reject the EU constitution in a referendum on 29 May.
Mr Chirac says the yes vote is the best possible choice for France
Rather than promoting a neo-liberal economic framework, as some voters fear, the constitution would enshrine French values, Mr Chirac insisted.
Neither left or right, the constitution would be what EU states made of it, but could only boost French power, he said.
He spoke as two polls suggested the Yes campaign was finally gaining ground.
However, two other polls still put the No vote ahead.
Responding to questions from two French journalists, Mr Chirac denied that the EU constitution would destroy the French social model and replace it with an Anglo-Saxon style economy.
On the contrary, he said, the treaty was "essentially of French inspiration" - it was "the best possible" choice for France.
He called the text the "daughter of 1989", the year the Berlin Wall fell, and "especially the daughter of 1789", referring to the French Revolution.
It would only increase French and German influence in Europe, ensuring that the two founding nations had a decisive say in the new, enlarged EU of 25, he said.
Mr Chirac gave a more polished and assured performance than in his previous TV appearance in a staged debate with students, when he appeared ill at ease, the BBC's Caroline Wyatt reports from Paris.
FRENCH EU POLLS
3 May: 51% Yes, 49% No (CSA for Le Parisien)
2 May: 48% Yes, 52% No (BVA for L'Express)
2 May: 53% Yes, 47% No (Ipsos polling group for Le Figaro/Europe 1)
2 May: 49% Yes, 51% No (Louis Harris for Liberation, Yahoo!, i-TELE)
30 Apr: 52% Yes, 48% No (TNS-Sofres/Unilog for Le Monde/RTL/LCI)
The previous 25 polls between 15 March and 29 April showed a majority for the No vote
But whether it was enough to persuade opponents of the treaty to vote Yes in this decisive phase of the French campaign is still unclear, our correspondent says. It is thought it will be French voters on the left who will need the most convincing, as many are tempted to use the referendum as a chance to punish Mr Chirac for high unemployment and a slowing economy.
Major political figures on the left and right are now backing the Yes campaign - but both sides still have everything to play for, with about 25% of the French still undecided.
A CSA poll for Le Parisien newspaper on Tuesday showed 51% intending to vote for the treaty, while an Ipsos poll for the newspaper Le Figaro and radio Europe 1 on Monday showed 53% of voters in favour of the treaty.
But a Louis Harris poll for newspaper Liberation on Monday showed 51% of voters still intending to vote against the treaty, while a BVA poll for L'Express magazine, also on Monday, put the No vote at 52%.
Twenty-five consecutive polls have pointed to a No vote, putting the opposition at between 51% and 62%.
The constitution has to be ratified by all EU member states, but many of them are not holding referendums.
The treaty is aimed at streamlining decision-making in the enlarged EU of 25 nations.