Left, right and centre: France's Presidential candidates

All three of them are insiders pretending to be outsiders. All three lost their fathers quite young. All three are fiftysomething - which counts as old in British politics but is startlingly young in France.

There are striking similarities between the two men and one woman who have a chance of being the Next Big Thing across the Channel. There are also telling differences.

Nicolas Sarkozy, 52, is the candidate of the centre-right party of government and the political "family", which has largely dominated power in France for 40 years. He wants to change the whole structure and psychology of French society, both the government and the governed. (Or at least he once did. His actual campaign has become a dreary festival of tough-on-crime, nationalist flag-waving, and other simplistic slogans.)

Ségolène Royal, 53, is the candidate of the Parti Socialiste, which has been the alternate tenant of power, and the occasional co-tenant, for the last 26 years. She wants to close the gap between government and governed; she wants to reconcile left-wing France with the free market. She wants "arrogant" but dysfunctional France to be more like modest, effective Sweden or Denmark. She is, herself, accused of being arrogant and dysfunctional.

François Bayrou, 55, is the candidate of the forgotten centre - re-branded "le sexy centre". M. Bayrou, a farmer's son who owns the most photographed old, red tractor in France, is running as a provincial outsider. He promises to sweep away the Parisian élites of right and left and install pragmatic, provincial values in the Elysée Palace. He forgets to mention that his party, the Union de la Démocratie Française, has been associated with many of the, essentially centrist, governments since 1974 (producing one President and two prime ministers). In the name of urgent change, he preaches "patience" and tractor-speed caution.

Any one of the three is likely to bring a refreshing shift in style, and maybe even substance, to the recent tradition of aloof but ineffectual government in France. Fifteen years after the US, 10 years after Britain, France is about to elect a leader who was born after the Second World War.

Nicolas Paul Stéphane Sarkozy de Nagy-Bocsa was born in Paris on 28 January 1955.

His father, Pal, was an aristocratic Hungarian charmer, a refugee from Communism and an advertising executive. His mother, Andrée, is a formidable, half-Jewish lawyer, who supported and raised Sarkozy and his two brothers after their father abandoned the family when Nicolas was 12 years old.

Nicolas and his wife Cécilia have a son, aged 11. Each have two children from previous marriages.

Unlike most French politicians, Sarkozy has not come through the traditional academic, finishing schools of the French élite, the Grandes Écoles. He qualified as a lawyer and learnt his politics at the grass roots - admittedly at the roots of very lush grass. He became mayor of his home town, Neuilly-sur-Seine, one of the wealthiest suburbs of Paris, at the age of 28.

Originally a protégé of Chirac - and briefly linked to Chirac's daughter, Claude - Sarkozy split with the Chirac clan in 1993-4. He supported Chirac's centre-right rival, Edouard Balladur, in the 1995 presidential election. Chirac won.

Sarkozy patiently built his own power base. He became a hyper-active, successful and popular interior minister after Chirac was re-elected in 2002. Only a year into the new term, he let it be known that, after 35 years of prominence but little achievement, Jacques Chirac was a man of the past. Sarkozy lifted himself up a whole division from one of a number of centre-right contenders for the presidential crown, to the contender. That took cunning, but it also took guts.

Under Chirac's considerable nose, Sarkozy stealthily made himself the most popular member - and then the leader - of the party founded by Chirac in 2002: the Union pour un Mouvement Populaire (UMP).

As interior minister, he made his reputation by acting and talking tough. Several weeks before the riots that swept through the poor suburbs of French cities in 2005, Sarkozy talked of multi-racial, suburban youth gangs as "scum". He promised to clear them out with a "Kärcher" or high-powered hose.

These events have been used by the Left in France, and many in the suburbs, to portray Sarkozy as an unstable and autocratic racist. He may be unstable and autocratic, but there is no evidence that he is racist. He is the only politician, on left or right, in France to call for positive discrimination for ethnic minorities.

President Chirac has always been convinced that Sarkozy could never be president. He is too short (five feet five inches), too frenetic and lacks the mystical-theatrical dimension needed to be head of state, rather than a mere head of government.

As Sarkozy's star rose, the Chirac clan did all in its power to shoot it down. In 2003-04, they tried to manipulate false allegations that Sarkozy was financially corrupt. In 2005, they leaked the news of a rift in the power marriage between Nicolas and Cécilia Sarkozy. All to no avail.

Sarkozy has been leading the opinion polls since mid-January. A couple of weeks ago, after sustaining hopes of another term almost to the end, Chirac finally gave his estranged former protégé the most chilling of endorsements.

Marie-Ségolène Royal was born in Dakar, Senegal, on 22 September 1953. She emigrated to France, aged two, when her father's military posting expired. The misogynist, authoritarian Colonel Jacques Royal later abandoned his wife, Hélène, and his eight children. Marie-Ségolène was left in considerable penury.

Abandoning her "Marie" prefix, she reached two of the finishing schools of the French elite - Sciences Po and the École Nationale d'Administration (ENA). She owed her success to brilliance and scholarships, not to family connections and financial support.

At ENA from 1978, her fellow-pupils included Dominique de Villepin, now the centre-right prime minister, and François Hollande, now the first secretary of the Parti Socialiste. M. Hollande is also her partner and the father of her two sons and two daughters, aged 15 to 24. They never married, by Mme Royal's choice.

At ENA she was regarded as the girlfriend of François, a young man destined for great things. He graduated ninth out of about 130 pupils; Ségolène was 95th.

Their political careers have run in parallel. He rose to be leader of the party. She had relatively junior ministerial posts and then became governor of the Atlantic Poitou-Charente region in 2003.

Her decision to run for the Socialist presidential nomination last year amused and irritated other party leaders, including François. Her success astounded them. She campaigned mostly outside the party as an open-minded, non-ideological socialist with conservative, family values. Mme Royal became so popular in the country at large that party members became convinced that she - and she alone - could defeat Sarkozy. They voted overwhelmingly for her as their candidate last November.

Since then, she has struggled, partly because she allowed herself to become too tangled in party doctrine; partly because many important figures in the party distanced themselves from her campaign. She also fell foul of dirty-tricks by the centre-right and of several self-inflicted gaffes: for example, she refused to distance herself from a Hizbollah politician who accused Israel of being a Nazi state, and she made throwaway comments about Corsica becoming independent.

In recent weeks, she has declared herself more independent of the party and adopted a series of more conservative and nationalist poses. Her poll ratings have started to rise again.

François René Jean Lucien Bayrou was born on 25 May 1951 in the village of Bordères in the Pyrenean foothills of south-west France. He is a farmer's son and a former teacher. He still lives and raises horses in his native village. Bayrou is a devout Catholic. He and his wife, Elisabeth, have six children.

As a young man, François had a crippling stutter. He cured it by reciting poetry to himself in front of a mirror. He was a brilliant student who might have gone on to a glittering academic career. His father, Calixte, was killed in a farm accident when François was 20 years old. He decided to combine a career teaching Latin and French in a lycée in Pau with running the family farm with his mother, Emma.

Bayrou likes to present himself as a home-spun man of the soil. This somewhat disguises the fact that he is the most intellectually gifted of the three main candidates. It also disguises the fact that he has been a substantial figure in national politics for the past 14 years.

Bayrou has written a series of highly acclaimed books on historical subjects, including a biography of the French king Henri IV (1553-1610), who tried to reconcile Catholics and Protestants. (Henri was assassinated for his pains.)

Bayrou's proclaimed mission is to reconcile left and right and create a centrist, pragmatic, consensual "third way" in French politics. Critics point out that almost all French politics for the past 25 years has been centrist and consensual. They also complain that Bayrou's party is not strong enough to win a majority in the parliamentary elections in June. A President Bayrou would be able to carve out a parliamentary majority, with votes from right and left, but it would be a majority to do nothing very much.

From 1993 to 1997, Bayrou was minister for education. He introduced one or two innovations but is mostly remembered for allowing the teaching unions to co-manage the ministry: not a formula for radical reform.

He has been the leader, since 1998, of the centrist Union pour une Démocratie Française (UDF), the alternative (ie non-Gaullist) centre-right alliance formed by President Valéry Giscard d'Estaing in the Seventies. Many of the more right-leaning members of the UDF agreed to join with Chirac's Gaullists in a Big Party of the Right, the UMP, in 2002. Bayrou stuck it out as head of a centrist rump of 30 UDF deputies in the Assemblée Nationale.

From late January, he surged in the polls, taking potential votes from Ségo-doubters on the left and then from Sarko-haters on the right. For the past couple of weeks, he has been treading water, but he should not be written off. If he reaches the two-candidate second round on 6 May, he would probably beat either Sarkozy or Royal.

Who will be the next President? Who should be the next President? Bayrou is the most likeable candidate. Royal is the most intriguing. Sarkozy is the candidate most likely to move France forward. He is also the candidate most likely to set France alight.

It hardly matters whether Sarkozy is the racist, ultra-capitalist portrayed by the left. (He isn't.) A President Sarkozy would be opposed in the streets by the unions and in the poor housing estates by the youth. Many on the French right doubt whether he has the temperament to see off such challenges calmly.

Mme Royal might be a more innovative Présidente than many people imagine. She might also be a calamity. Her main problem would be the dearth of people within her own party who agree with (or even understand) her proposals to "Scandinavianise" France.

Bayrou, the unlikely challenger, is also the man who would most comfortably fit the mould of father-confessor of the nation. He is avuncular and charming like Chirac; erudite and cultured like Mitterrand. He is also the candidate who would be most likely to allow France to drift for another five years.

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