A poll showed on Sunday that Socialist candidate Francois Hollande would still comfortably beat French President Nicolas Sarkozy in a run-off.
Sarkozy has been capitalising on his central role in Europe's struggle to contain its debt crisis, and gained ground even after announcing plans for an unpopular sales tax hike and after Hollande's campaign took a more aggressive tone.
In the first round of the two-stage vote, on 22 April, Hollande would win 28 per cent of the vote while Sarkozy would secure 26 per cent, the poll by IFOP for weekly newspaper Le Journal du Dimanche found.
Hollande had a 10-point first-round lead shortly after the Socialist Party chose him as their candidate in October.
In the run-off, the poll showed Hollande winning with 54 per cent of the vote while Sarkozy would get 46 percent, also the smallest margin registered so far in the election race and down from 20 percentage points in October.
Sarkozy hopes that, in the 6 May run-off, he can pick up ballots from people voting for far-right candidate Marine Le Pen and centrist Francois Bayrou in the first round. Pollsters say many of those voters have not decided yet who to pick in the second round.
Sarkozy, widely expected to announce in February that he is seeking a second mandate, has been gaining momentum in opinion polls even though his economic credentials are under fire, with France at risk of losing its AAA credit rating and unemployment running at a 12-year high.
The president is putting a new focus on spurring growth and reviving French companies' competitiveness. In a political gamble, the government said it would finance a cut in social welfare contributions paid by large companies with an increase in sales tax.
Hollande has stepped up his attacks on Sarkozy, accusing him in an open letter of running the economy onto the rocks and being a "president of the privileged".
The IFOP poll was based on telephone interviews between 4 and 6 January with 1,163 people registered to vote.