The populist Swiss People’s Party, which has the most seats in parliament, has stirred up and fostered anti-migration sentiment over the years, notably about an influx of workers from the neighboring European Union.

Some have dubbed the proposal a “Swiss Brexit” because it could jeopardize Switzerland’s deep ties to the European Union anchored by deals that foster economic growth, cultural ties and cross-border travel, among other things. Switzerland is not one of the EU’s 27 member states, but it is all but surrounded by four of them

Recent polling from the gfs.bern agency suggested that it could be a close contest.

Preliminary results shared by the federal government showed that nearly 53% of voters rejected the proposal, with nationwide turnout exceeding 57%. Results were still pending from many of Switzerland’s 26 cantons.

The number of people living in Switzerland has soared by nearly one-quarter over the last generation, and foreigners today make up nearly one-third of the population.

Critics say the boom in migration has brought foreign labor and skills to sectors such as healthcare, finance, pharmaceuticals, and technology.

The right-wing party put forward the “sustainability initiative” measure, saying Swiss infrastructure, housing, social programs, natural resources and way of life have been strained by the spike in demographic growth.

The federal government, Parliament and EconomieSuisse, a major business association, oppose the idea.

In Geneva, Switzerland’s second-largest city and a hub of U.N. institutions and humanitarian groups, early results showed about two-thirds of voters in the region opposed the measure.

Maria Lalu, a former diplomatic mission worker from the Philippines who arrived in Switzerland in the early 1980s, said she supported the proposal. “I have nothing against immigration. I also am a stranger,” she said after casting her vote, adding that she wants immigration to be more orderly.

Schoolteacher Natascha Robert said she voted against the bid, expressing concern that approval could hurt Switzerland’s relationship with the EU. She also said Switzerland’s growing diversity is an asset.

“I think people always have something to bring us,” she said outside a polling station in the central Paquis neighborhood, emphasizing that she was born in Switzerland to two Swiss parents. “Does that mean that we have more foreigners, I feel less Swiss? Really, not.”

Swiss democracy gives voters a direct say in policymaking through referendums typically held four times a year. Most ballots are cast through the mail, and in-person voting ends at noon local time on Sunday.

A “yes” vote would require the Swiss government to take action to cap the population by 2050.

If the population reaches 9.5 million before then, the government would be forced to restrict asylum, family reunification and residency permits, and may have to scrap Switzerland’s EU deal on the free movement of people.

The Organization for Economic Cooperation and Development has reported that Switzerland had a foreign-born population of 32% as of 2024, behind only Luxembourg and Australia among the group’s 38 member countries.

International migration has long been a sensitive issue in Europe, as nations grapple with an aging population and increasing anti-foreigner sentiment. While that sentiment in other European countries centers on migrants from the developing world, most foreigners in Switzerland are Europeans.

Since Switzerland and the EU eased restrictions on citizens living and working across their borders in 2002, the Swiss population has grown by 23%, to 9.1 million as of the end of last year. Economic output has also increased, up 24% over the same period, government data show.

Swiss voters have repeatedly tackled the immigration issue over the last half-century. Only one such referendum — “Against mass immigration” in 2014 — narrowly passed, after campaigners stoked fears about overpopulation and rising numbers of Muslims in the country.

While many countries have limits on immigration, none has ever voted to limit its population, Swiss experts say.