Mr Sarkozy, the former interior minister and leader of the ruling conservative UMP, is favourite to become president on 6 May.

Why does the election matter?

France gives its president real power, unlike many other states, where the prime minister is the key figure. Far from being a figurehead, the French leader chooses the prime minister, can dissolve parliament and can pardon convicted criminals. The president is also commander-in-chief of the armed forces, including a formidable nuclear arsenal.

Were there any surprises in the first round?

The exit polls were broadly in line with most opinion polls in the run-up, but Francois Bayrou of the centrist UDF, the junior partner in the coalition, did not make the breakthrough that at one stage seemed possible. But his 18.3% was much stronger than his result in 2002.

Jean-Marie Le Pen, leader of the far-right National Front, got 11%, according to initial results - less than many had expected. He had shocked France by reaching the second round in 2002.

What does the first round outcome mean for the second round?

The 6 May run-off vote is by no means a foregone conclusion for Mr Sarkozy, even though he scored an impressive 30% in the first round, according to initial results.

Ms Royal got nearly 25% - a relief to Socialists who were humiliated by Mr Le Pen's success in 2002. She is likely to get support from those who voted for her left-wing and green rivals.

The big question is which way Mr Bayrou's voters will turn in the run-off - left or right? He could play the role of kingmaker before the second round. Either way, his influence on whoever becomes president will be significant. Mr Bayrou's call for a new centrist consensus may give him some leverage over the next president, as this election is seen as a clear break with the traditional left-right split in French politics.

The huge turnout - likely to be repeated on 6 May - should give the next leader a powerful mandate.

Who were the other contenders?

Other candidates included the leftists Olivier Besancenot, Marie-George Buffet and Arlette Laguiller, the conservative Philippe de Villiers, the anti-globalisation farmer Jose Bove and Dominique Voynet of the Greens. Altogether 12 candidates contested the first round. The current president, Jacques Chirac, did not stand.

How is the 2007 race different?

For the first time, one of the top candidates is a woman. Segolene Royal's bid has ignited a debate about the place of women in a country traditionally dominated by men. Nicolas Sarkozy, 52, would be the youngest president since Valery Giscard d'Estaing won in 1974 at the age of 48 - Jacques Chirac and Francois Mitterrand were both in their 60s when they entered the Elysee Palace.

What are the main campaign rules?

Candidates are accorded strict equality in terms of air time on radio and television. Each one has 45 minutes of broadcast time. They can use three types of campaign clip: one-minute, two-and-a-half minutes and five-and-a-half minutes. From 20 April no opinion polls could be published ahead of the first round. Similarly, opinion polls are banned in the two days before the second round on 6 May. Each candidate has a campaign spending limit of 16.16m euros (£11m; $22m) in the first round. The limit for each of the two candidates in the second round is 21.5m euros.

What are the national issues?

Unemployment of 8.4%, sluggish economic growth, political sleaze, unrest among disaffected ethnic minorities, discontent with the EU, continuing divisions on the French left.

What are the personal issues?

Segolene Royal's bid has been dogged by questions over her qualifications for the job as she has never held any of the big ministries of government. Apparent foreign policy gaffes have damaged her credibility. Nicolas Sarkozy's political experience is not in doubt but he was accused of taking an unfair advantage by remaining interior minister - a high-profile and influential post - until relatively late in the campaign.

Top soundbites?

"Together everything is possible," says Sarko on his official campaign website. "A fairer France will be a stronger France," says Sego on hers. Francois Bayrou envisages "a France of all our forces". Jean-Marie Le Pen looks to "the victory of France and the future of the French". "We want a shining France" - Philippe de Villiers. "Our lives are worth more than their profits" - Olivier Besancenot. "France has never been so unequal" - Jose Bove.

Can we forget about French politics after 6 May?

Not quite. A parliamentary election will be held on 10 and 17 June. A candidate must take an absolute majority in their constituency to win in the first round. Otherwise, if they get at least 12.5% of the first-round vote, they go through to the second round, where only a simple majority is needed to win. Parliament is currently dominated by the UMP.