Last weekend, in European Parliament elections, the body’s far-right bloc made strong gains across the Continent.

Nowhere was the revolt against the political establishment more alarming than in France, where Marine Le Pen’s National Rally so thoroughly trounced President Emmanuel Macron’s centrist Renaissance—winning more than twice as many seats—that Macron announced a snap election for the National Assembly just weeks before the summer Olympics come to Paris.

Next door in Germany, a country whose postwar culture of Holocaust memory and political stability managed to prevent the far right from entering the Bundestag for more than 70 years, the nationalist and xenophobic Alternative für Deutschland (AfD) came in second.

Meanwhile, Italian prime minister Giorgia Meloni’s Brothers of Italy—ideological heirs to Benito Mussolini, several of whose descendants have run for office under its banner—more than doubled its seats.

All three parties have appealed to voters primarily on the issue of immigration, which they pledge to dramatically reduce, if not stop altogether. The election offers lessons for America, where voters rank not Palestine, abortion, or even inflation, but immigration as their top issue and are heading to the polls this fall.

In short: it’s the border, stupid.

One takeaway is that, when campaigning against the far right, warnings about Fascism no longer work, especially among young voters. In Germany, 16 percent of young voters chose the AfD. In France, 32 percent of 18-to-24-year-olds chose the National Rally, while only 5 percent went for Renaissance. Jordan Bardella, the charismatic 28-year-old president of the National Rally and its lead candidate in the European Parliament elections, lacks the baggage of the party’s founder (and Marine’s father), Jean-Marie Le Pen, who infamously called Nazi gas chambers a “detail” of history.

The traditional approach of stigmatizing far-right parties by invoking their authoritarian roots is having little effect on generations for whom Auschwitz, Vichy, and D-day are obscure references in a history book—one they may not have cracked open.

Another lesson is that responding judiciously to voter concerns about migration, rather than labeling them “racist” or the product of “misinformation,” can strengthen support for the political mainstream. While Social Democratic and Liberal parties fared poorly on Sunday, the European People’s Party (E.P.P.), the pan-Continental coalition of center-right parties, gained seats and maintained its position as the largest faction in the legislative body. Earlier this year, the E.P.P. led the initiative to approve a package of policies aimed at reducing the number of migrants entering Europe.

Stigmatizing far-right parties by invoking their authoritarian roots is having little effect on generations for whom Auschwitz, Vichy, and D-day are obscure references in a history book—one they may not have cracked open.

One country where the far right has been kept safely at bay is Denmark. Not coincidentally, parties across the political spectrum there have, since the migrant crisis of 2015–16, implemented a series of hard-nosed policies aimed at deterring immigrants from outside Europe and integrating those who already live there. The country’s ruling Social Democratic Party has continued the policies of its centrist predecessor, and immigration has essentially become de-politicized. What passes for far-right parties in Denmark have only 23 of 179 seats in the Danish Parliament, and 2 out of 15 seats in the country’s delegation to Brussels.

Fortunately, some leaders are belatedly waking up to the costs of uncontrolled immigration. Last fall, after demonstrators—many of them immigrants—took to the streets of Berlin to celebrate the October 7 Hamas massacre, Germany’s Social Democratic chancellor Olaf Scholz said, “We must finally deport on a large scale those who have no right to stay in Germany.” He was joined by his vice chancellor, a member of the Green Party, who released a video criticizing Muslim organizations for failing to speak out against anti-Semitism, and threatened to deport those who commit anti-Semitic hate crimes.

American politicians would do well to watch what’s happening in Europe. Here in the United States, a slight majority of the public supports mass deportations of illegal immigrants, including 42 percent of Democrats, 45 percent of Latinos, and 35 percent of Gen Z. Left unaddressed, the crisis at the southern border will become an even greater issue for unscrupulous politicians to exploit. And while President Joe Biden may have signed an executive order earlier this month tightening the border, it may be too late. A recent CNN poll found that voters trust Trump over Biden on the issue by a 27-point margin.

Reeling from last Sunday’s election, a seasoned observer of international affairs told me that he expects Le Pen to win France’s next presidential election, in 2027. Her party already has a massive lead in the fast-approaching legislative election, and the momentum propelling her towards the Élysée Palace may be unstoppable.

This would put into power a party that is not only anti-immigration but pro-Putin, lukewarm towards NATO, and suspicious of the United States. To preserve the liberal world order, mainstream political parties across the West need to absorb the message that voters have been sending them and adopt tougher policies on mass immigration. Because if they don’t, demagogues and would-be dictators will.

James Kirchick is a Writer at Large at AIR MAIL and the author of The End of Europe: Dictators, Demagogues, and the Coming Dark Age