IT IS an unwritten rule of French politics that presidents must distance themselves from the Paris elite. François Mitterrand had roots in Cognac and then Burgundy; Jacques Chirac planted them in rocky Corrèze, in south-central France. So it is for today's candidates. François Hollande, a Socialist, has also adopted Corrèze, where he is a deputy. Nicolas Sarkozy, the centre-right incumbent, who hails from the posh Paris suburb of Neuilly, has a Hungarian background and did not go to the best French schools.

It is odd, then, that four of this year's presidential aspirants graduated from the same elite training college, the Ecole Nationale d'Administration (ENA): Mr Hollande, Dominique de Villepin on the independent centre-right and two fringe candidates. Stranger still, Mr Hollande and Mr de Villepin are both from the class of 1980, known as the promotion Voltaire—as is Ségolène Royal, Mr Hollande's ex-partner and the Socialists' defeated candidate in 2007. (The three are circled in the picture, above.)

That a single graduating class of about 80 French students has such a political grip shows how the country manufactures its ruling class. Other 1980 ENA alumni include Jean-Pierre Jouyet, head of the financial-markets regulator, who is tipped for a senior post in a Hollande presidency; Henri de Castries, head of AXA, an insurance giant; Pierre Mongin, head of the Paris metro; and a clutch of mere ex-ministers and ambassadors.

So-called énarques, who tend to be fiercely clever and answer questions with the phrase “There are three points,” shrug off accusations of elitism. The college selects its students on merit in a competitive exam, and tuition is free. ENA was set up in 1945 as a meritocratic institution meant to produce a post-war administrative elite. Yet since about 1980, fewer people from poorer backgrounds have got in. The share of working-class students at the top four grandes écoles, including ENA, fell from 29% in the 1950s to 9% in the mid-1990s, finds one study.

All countries have ivy-league schools, but the hold of ENA on top jobs in France is breathtaking. Seven of the past 12 prime ministers were énarques. Senior officials shuffle into business too. Of 600-odd French senior bosses, 46% come from one of three grandes écoles, including ENA, according to research by two academics. Alexandre de Juniac, ex-chief of staff for Christine Lagarde as finance minister, is head of Air France; another ex-chief of staff, Stéphane Richard, runs France Telecom. François Pérol, former chief of staff to Mr Sarkozy, runs Banque Populaire Caisse d'Epargne.

Several grandes écoles have tried to widen their intake. In 2009 ENA set up a scheme to prepare low-income students for the entrance exam. But progress is slow. The first student from the course has only recently won a place. Meanwhile, ENA alumni are not only resurgent in the presidential race. Mr Sarkozy's government, which five years ago had just two énarques, is ending with six.