After opinion polls in Britain and the United States were criticized, fairly or not, for failing to foresee British voters’ decision to leave the European Union and the election of Donald J. Trump, French pollsters could be forgiven for showing Gallic pride.
Despite a political earthquake in France that saw the upending of the traditional divisions between left and right, polling companies managed to predict the outcome of the first round of France’s presidential election on April 23 with a remarkable degree of precision. For the most part, they correctly forecast that Emmanuel Macron, a former economics minister, and Marine Le Pen, a nationalist firebrand, would progress to the second round, as well as the order of the three runners-up, within a percentage point or two.
“This first round is the revenge for the polling institutes,” proclaimed Paris Match, the popular French magazine. “Criticized since Brexit and the election of Donald Trump in the United States, they showed that they haven’t lost their clairvoyance when it comes to French politics.”
How did the French pollsters get it right when pollsters in other countries have not?
Anthony Wells, research director at YouGov, a leading British polling company, said that while pollsters across the world had been struggling to forecast the impact of rising populism in this era of disgruntled voters, French pollsters had an advantage because Ms. Le Pen’s party, the National Front, had been active in France for decades, giving them comparative data from previous elections.
The need to take the National Front seriously was made clear in 2002, when Ms. Le Pen’s father, Jean-Marie Le Pen, shocked the country and confounded pollsters by making his way into a runoff for the presidency at the expense of a sitting prime minister, Lionel Jospin. Socialists held their noses — some literally with clothespins — and supported the center-right candidate, Jacques Chirac, dealing Mr. Le Pen an emphatic defeat.
Polling experts said French pollsters had also benefited from a robust turnout of 78.7 percent in the first round.
“If the voters pollsters talk to turn out in force, there is less risk of getting it wrong,” said Prof. Leighton Vaughan Williams, director of the Political Forecasting Unit at Nottingham Business School.
Several French pollsters also credited their success to the widespread use of online polling. While the practice has its critics, some pollsters say people are more likely to acknowledge that they are voting for a far-right party like the National Front if they are doing so by clicking a box on a website rather than if they are being asked by a stranger over the phone.
“In online polling you guard against the problem of hidden voters, who don’t want to admit to a stranger who they are voting for,” said Frédéric Dabi, the director general of Ifop, one of the country’s leading polling companies.
Getting the polls right initially appeared daunting for many pollsters. In the 16 weeks leading up to the first-round vote, assessing the prospects of a fragmented field of 11 candidates, including Jean-Luc Mélenchon, a leftist, and François Fillon, a center-right candidate hit by scandals, appeared so fraught that the newspaper Le Parisien, which regularly runs polls, decided not to run any.
Adding to the challenges for pollsters, Mr. Macron was running without a political party and some doubted that his new movement could mobilize voters. Mr. Fillon, initially the front-runner, became mired in a corruption scandal. Mr. Mélenchon surged after a televised debate. Then, less than 36 hours before the polls opened, a gunman killed a police officer on the Champs-Élysées, potentially influencing the election.
“We were worried before the election because this was not a traditional election between left and right, and there was a large element of unpredictability,” said Bruno Jeanbart, the deputy managing director of OpinionWay, a leading Paris-based polling company.
But the results largely mirrored the polls. On April 21, the last day forecasts were published ahead of the vote, an average of eight major polls assembled by OpinionWay put Mr. Macron at 24 percent, Ms. Le Pen at 22.4 percent, Mr. Fillon at 19.4 percent and Mr. Mélenchon at 18.9 percent. The final results: 24 percent for Mr. Macron; 21.3 percent for Ms. Le Pen; 20 percent for Mr. Fillon; and 19.6 percent for Mr. Mélenchon.
Looking to the second round, the candidates are offering diametrically opposed visions of France. While Mr. Macron, a former banker, favors economic liberalism and more European integration, Ms. Le Pen rails against immigrants, globalization and the European Union.
French pollsters say they are confident they can replicate their success in the first round and are predicting that Mr. Macron will win by as much as 20 percentage points.
OpinionWay has been predicting that Mr. Macron will get 59 percent of the vote compared with 41 percent for Ms. Le Pen. Mr. Jeanbart said he was confident about that forecast because fewer than a tenth of voters aged 65 or older, who tend to support the European Union, had voted for the Ms. Le Pen in the first round, and they constitute a quarter of registered voters. He also said it was easier to predict the performance of two candidates compared with 11.
But voters around the world are learning to be wary of certainties, and some analysts see a path to victory for Ms. Le Pen if her motivated supporters turn out in force and enough of Mr. Macron’s supporters stay home.
Mr. Dabi of Ifop warned against those professing to have political crystal balls. “It is idiotic to say that Macron will win when the campaign is still on,” he said, adding, “We are not clairvoyants who can predict the future.”