BRUSSELS — Europe has been struggling for years to limit the number of migrants illegally entering by land and sea, instituting increasingly tough policies. Those moves now appear to be working, with the numbers of migrants crossing into European Union countries decreasing dramatically from highs last year.

But despite the decline in migrant arrivals, anti-immigrant sentiment is flourishing, with leaders adopting or considering harsher policies that mainstream political parties would have balked at a few years ago.

As in the United States, the steep drop in border crossings has done little to diminish the political potency of the issue.

In Italy, Prime Minister Giorgia Meloni is trying to send migrants rescued in the Mediterranean to Albania. Germany, one of the most welcoming countries during the wave of migration in 2015, has extended patrols to all its land borders. And Poland plans to introduce legislation to temporarily suspend the right of new arrivals to ask for asylum.

The crackdowns have been driven in part by xenophobic, anti-immigrant political parties that have played on fears of uncontrolled migration and a dilution of national identity. Their arguments are gaining a more receptive audience with Europeans who worry that the influx of migrants is unmanageable and who are frustrated that about 80% of failed asylum-seekers never leave, according to EU data.

Their leaders, some of them facing elections, have taken note. In Germany, the Christian Democrats — the party of former Chancellor Angela Merkel, who famously welcomed immigrants in 2015 — have been pressing hard for tougher measures to control illegal immigration and is leading in the polls.

“The far right is the mainstream when it comes to migration now,” said Susi Dennison, a senior fellow at the European Council on Foreign Relations in Paris.

What do tougher measures look like?

Europe has tried many methods over the years to limit migrants from arriving illegally, including controversial programs that paid such countries as Libya and Turkey to stop them from taking rickety boats out to sea.

Other measures were seen as either too harsh or potentially illegal. A 2018 EU report outlining options concluded that sending asylum-seekers to third countries without processing their requests was not permitted under EU and international law.

So it was a sign of how far the discussion has moved to the right when Ursula von der Leyen, president of the European Commission, praised Italy’s plan to send migrants to Albania as “out-of-the-box thinking.” Under Meloni’s plan, migrants would be screened in Albania and stay in detention centers while they await decisions on their asylum applications.

That plan has been held up by an Italian court that questioned whether asylum-seekers from possibly unsafe countries could be held in Albania.

Other ideas floated by European leaders would involve paying countries outside the bloc to process asylum applications and take on the responsibility of deporting those whose claims fail. Human rights groups have questioned the legality of such programs.

Britain unsuccessfully tried a more extreme approach, attempting to send asylum-seekers to Rwanda for processing and resettlement. Even those whose claims were accepted would never have been allowed to settle in Britain. The country’s Supreme Court ruled the policy illegal.

Other countries, including Poland and the Netherlands, are, like Germany, intensifying border controls.

Those increased border checks appear to be making a difference — and having something of a domino effect.

What is driving the anti-immigrant backlash?

One reason is the sheer numbers of migrants over the past decade and the failure of many governments to integrate them effectively. Some of the blame is placed on extremist parties exaggerating the problem and the dangers. As they have attracted voters, they have also pushed more centrist parties to take a harder line.

Although the numbers of migrants illegally attempting to cross into the EU dropped 43% in the first 10 months of this year compared with the same period last year, that follows a year in which the bloc experienced its highest number of such crossings since 2016. At that time, Europe was in the throes of a migration crisis driven in part by more than 1 million Syrian and Afghan refugees fleeing war.

According to Frontex, the EU’s external border agency, there were about 380,000 irregular border crossings into the bloc in 2023.

In addition, more than 4 million Ukrainians have been offered temporary protection in the EU since Russia’s full-scale invasion in February 2022.

Also driving outrage is the failure to deport rejected asylum-seekers, a task that can be complicated.

Often the migrants’ countries of origin refuse to take them back, especially if the people destroy the paperwork proving where they were born. While the deportation process drags on, migrants can move undetected to other countries in the bloc since there are few restrictions on travel between many European nations.

The anger over failed asylum-seekers boiled over in Germany in August, after a Syrian whose application for asylum had been rejected confessed to fatally stabbing three people and wounding eight at a festival in Solingen. The attack happened just months after a police officer was killed in a knife attack in Mannheim; the Afghan man indicted in that case had been denied asylum but then married a German so was in the country legally.

Germany has been successful in integrating many of the refugees who came in 2015 and 2016, but for many Germans, the attacks added to worries that immigration was costing too much when the economy is flagging.

What happens next?

For now, Europe remains frozen in its attempts to balance the economic necessity for more workers, the concerns of its citizens over migration and the need to abide by long-standing European laws meant to protect refugees.

In Italy, Meloni has appealed the court’s ruling against her outsourcing plan. For now, the detention centers in Albania remain empty.

One thing the EU has been able to address is the long-standing demand for more countries to share the burden of accepting or caring for migrants, but even that plan does not come into effect until 2026.