Un Cheval de Troie fois 1000!

When the French put a draft Constitution for a newly enlarged European Union to a referendum in 2005, Pascal Verrelle voted passionately against it, hoping it would stop the European Union in its tracks. He rejoiced when the effort failed, yet was dismayed when the bloc kept gathering more members and powers, anyway.

At the time, Mr. Verrelle, a former soldier, was a prison director, but he eventually felt compelled to enter politics and joined the far-right National Front. When he was elected mayor of this small town in Provence eight months ago, the first thing he did was to take down the European Union flag from City Hall.

“In 2005, a majority voted against Europe, and we still find ourselves in Europe, by magic,” he said, “and I find it inadmissible.”

Today the European Union is wobbling under the weight of problems encouraged in part by that unchecked expansion — stagnant economies, the euro crisis and deep strains over migration, especially from newer members in Central and Eastern Europe.

But a visit to Le Luc and other villages in southern France is a reminder that the European Union faces yet another serious problem long in the making — a crisis of legitimacy — that is fueling right-wing, nationalist politics even in the traditional core of the bloc.

For Mr. Verrelle, 2005 was a watershed. Since then, opposition to a much-enlarged, poorer and vastly more diverse European Union has only increased. So has support for the National Front and its leader, Marine Le Pen, who has emerged as a serious contender in France’s presidential race.

Having already suffered a “Brexit” vote this year in Britain, Europe faces a series of critical elections in the year ahead. But none is more important than the vote in France, a founding European Union member.

The British decision to quit the European Union was a major blow, but a victory by Ms. Le Pen could be the death knell. And with the election of Donald J. Trump in the United States, that prospect has taken on new weight.

“Donald Trump makes Marine Le Pen sound reasonable,” said François Heisbourg, a special adviser to the Foundation for Strategic Research in France and chairman of the International Institute for Strategic Studies. “His victory gives her respectability. Everyone knows she’s not Trump — she knows how to use a noun and a verb and is intellectually coherent about what she wants and doesn’t want.”

What Ms. Le Pen wants is to lead France out of the euro currency and out of the bloc. She has said she would hold a popular referendum, à la Britain, on French membership in the European Union — a test of public will that mainstream French politicians, she says, are afraid to have.

“In 2005, a majority voted against Europe, and we still find ourselves in Europe, by magic, and I find it inadmissible” said Pascal Verrelle, the mayor of Le Luc and a member of the National Front.CreditDmitry Kostyukov for The New York Times

From the mood here in southern France, a “Frexit” push would probably prevail in a referendum, just as 55 percent voted in 2005 against the Constitution that a former French president, Valéry Giscard d’Estaing, had drafted.

The French “non” killed the treaty, intended to create new federal institutions for a bloc enlarged the year before by 10 countries, mostly former Soviet-bloc countries like Slovakia, Poland, the Czech Republic and Hungary.

“In a way, Frexit already happened,” said a prominent regional Socialist member of Parliament, Jean-David Ciot. “Europe did not keep its promises, to create a world of wealth and full employment.”

“People feel peace has been attained but fear that the rest of the world has come to undermine this wealth,” Mr. Ciot added. “They fear Europe is not protecting them from these migrants who come to pillage and steal their wealth.”

Brexit, he said, is “just a symptom of the rest — the feeling that we no longer share a common destiny.”

Since 2005, said Mr. Verrelle, southern France has been shifting steadily toward the National Front and its opposition to the European Union. In the last three elections, he said, “support has been growing systematically.”

The former prison director is scathing about the radicalization of young French Muslims and the dangers he says he believes that uncontrolled immigration poses to France.

“When I saw the prayers in the corridors of the prison, and others hiding their crosses, I knew we were lost,” Mr. Verrelle said. “What’s most dangerous about Europe is the loss of borders, and today we see the result,” he added, speaking of terrorist attacks and migrant flows.

“I’m worried about Daesh,” he said, using an Arabic acronym for the Islamic State. “We’re bringing in a Trojan horse times 1,000.”

As for the European Union, it has no clear political direction, Mr. Verrelle said, adding that it is too diverse economically for a single currency and too weak to allow freedom of travel.

 “We’re in Europe against our will,” he said. “It’s a prison. It’s not a solution that will last.”

About 90 minutes away, in La Tour d’Aigues, overlooked by the ruins of a Renaissance castle demolished during the French Revolution, Ms. Le Pen’s National Front organized a protest against plans to bring about 30 teenage asylum seekers from Afghanistan to the nearby town of Grambois.

The protesters, fewer than 200, were met by about 300 counterdemonstrators holding up banners showing solidarity with the refugees, while 90 riot police officers, dressed in black protective clothing, ringed the two groups to keep them apart.

Marion Maréchal-Le Pen, a niece of Ms. Le Pen’s and a rising star of the National Front, addressed the crowd from a makeshift podium, tossing her blond hair behind her.

“It is not the hate of others, it is love for Provence, love for France,” Ms. Maréchal-Le Pen, 27, shouted into the microphone, as counterprotesters whistled and booed to try to drown her out. She railed against a “dictatorial” European Commission that “works to undermine national sovereignty.”

Asylum seekers coming to France receive generous payouts, she said, while the Vaucluse region, the home of La Tour d’Aigues, is the sixth poorest in France, where one in five people are without jobs.

“We are against this completely crazy plan to redistribute migrants,” Ms. Maréchal-Le Pen said in a brief interview after her speech. The European project “is a failure,” she said. “We need to build another Europe.”

The wave of anger and identity politics is washing over France, with the ready-made instrument of a modernized National Front under Ms. Le Pen.

She has now become both a symbol and an agent of a kind of defensive French nationalism that is proving very popular, especially in the southwest and north, near the Belgian border.

As the European Union struggles with fundamental issues of coherence, policy and solidarity, she has also become a plausible, if unlikely, president of France, almost sure to make the two-candidate runoff for the post in May.

Brussels is an easy target, especially for politicians like her seeking to blame domestic ills on some supranational agency.

“There is huge disappointment with Europe,” said Sylvie Goulard, a French member of the European Parliament for this region. “But a tendency to blame Europe for national competencies — hospitals and nurses, malaise of the police, housing — these are all Franco-French failures, nothing to do with Europe.”

The mood is worse in the south, Ms. Goulard said. “I’m from the south, and people are angry and frustrated,” she said, “but you realize that lack of transportation or the failure to integrate foreigners are not the fault of Europe, but Le Pen is exploiting these issues.”

But even Ms. Goulard, who has announced her candidacy to become speaker of the European Parliament, acknowledges Brussels’s many failures. It has not created functioning external borders, and its response to the migrant issue has caused severe strains among member countries and undermined solidarity.

“It would be stupid to be too optimistic,” Ms. Goulard said. “But we have tried to do something never done on earth, to get so many people to live and trade together in peace.”

There are some strong proponents of Europe, too.

Alain-Pierre Merger, president of the Maison de l’Europe de Provence, the regional chapter of an association that supports the European Union and promotes European citizenship, said that it would be a tragedy to break up the union, and that young people now feel a European identity that must be strengthened. “Europe is an idea, but it must be seen to be working,” he said.

One of the members of the chapter, Caroline Brun, 23, said: “This has been a tough year for our hopes.”

Many blame Europe for the migrants, she said, adding: “But it’s not Europe. It’s the fault of the politicians of European states who use Europe as a scapegoat.”

At La Tour d’Aigues, even the town’s Socialist mayor, Jean-François Lovisolo, expressed disenchantment. Europe has “failed to fight for a European identity,” he said.

The monetary and economic union that underpins Europe did not translate into a closer political and social union, he said, “and Europe is not working.”

Ms. Le Pen’s supporters could not agree more. Édouard, a former colonel who served in Kosovo who declined to give his surname, said at the rally that “we have not seen the benefits” of Europe.

“My generation was told, ‘You are European,’ and there was great hope and excitement,” he said. “But that translated into a recession. It has been a terrible disappointment.