"There are 24 hours left in which the French are going to reflect.
Mar 16: Deadline for presidential candidates to get at least 500 mayors or other elected representatives to sponsor them. Without these, candidates cannot stand.
Mar 19/20: Constitutional Court examines proposals, decides list of official candidates.
Apr 9-20: Official campaign period.
Apr 21: First round presidential voting in overseas territories and departments. Guadeloupe, Martinique, Guyana, Saint-Pierre-et-Miquelon and French Polynesia.
Apr 22: First round of voting on mainland France, the Indian Ocean islands of Reunion and Mayotte and in New Caledonia.
May 5: Second round of overseas voting.
May 6: Second round of mainland voting.
May 17: End of President Chirac's mandate.
Jun 10: First round of parliamentary voting.
Jun 17: Second parliamentary round.
Jun 19: End outgoing parliament.
They know they are going to write a very important page in the history of France," said Royal, who is seeking to become France's first woman president.
A campaign blackout and poll embargo came into force at midnight on Friday and the final flurry of opinion surveys provided mixed messages to all four leading candidates.
The BVA and Ipsos institutes showed Royal had continued to narrow the gap slightly on Sarkozy but forecast that the former interior minister would go on to win a May 6 run-off against the Socialist by 52 per cent and 53.5 per cent respectively.
However, a CSA poll for the Le Parisien daily made the race a dead heat and put far-right leader Jean-Marie Le Pen in third place, ahead of centrist Francois Bayrou.
Polling stations open on Sunday after a day for reflection on Saturday with a dozen candidates seeking election.
"The election campaign has run against a background of fears over jobs, immigration and security"
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If, as expected, no one wins an absolute majority on Sunday, the top two will contest a second round ballot two weeks later.
In 2002, Le Pen stunned France by knocking out the Socialist candidate to win a place in the run-off against Jacques Chirac, the outgoing president who secured a comprehensive victory.
The election campaign has run against a background of fears over jobs, immigration and security, and attacks on camera crews in a flashpoint suburb revived still fresh memories of riots in France's deprived suburbs in 2005.
Police say no special anti-riot measures have been ordered for polling day beyond standard voter station security. But officials could ban the purchase of petrol in jerry cans - a measure imposed during the 2005 riots - if warranted.