Under French electoral law, candidates need at least 500 of France's 42,000 elected representatives, including parliamentarians and mayors, to contest the ballot.
Hunt for signatures
So far, seven candidates have enough signatures to run, including conservative frontrunner Nicolas Sarkozy, Socialist Segolene Royal and rising centrist Francois Bayrou.
Despite gaining 16.8 per cent in 2002, a score that saw him through to a run-off ballot won by incumbent Jacques Chirac, Le Pen's National Front has no mayors and party workers have been forced to search across France in the hunt for signatures.
Smaller parties have accused the mainstream parties of seeking to shut them out of the election to avoid a repeat of 2002 when are record 16 candidates helped dilute the vote for leading candidates and push Lionel Jospin, Socialist candidate and then prime minister, out of the race.
The Socialists and the ruling UMP party ordered their mayors not to sponsor rivals and independent officials say they faced heavy pressure to shun extremists.
Sponsorship of a candidate is not necessarily an expression of support and could simply mean they recognise the candidate represents a legitimate strand of opinion.