The posters seen in several cities and provinces featured two very similar young women: both born in Switzerland, educated in Swiss schools, now in their 20s and working full time in Swiss jobs. They even share the given name Vanessa.

The point, though, was the crucial way they differ. One Vanessa is a Swiss citizen, while the other is not, and is locked in a lengthy and expensive process to obtain citizenship even though her family put down roots in Switzerland two generations ago.

The posters backed a government-sponsored measure that would ease the path to citizenship for third-generation immigrants like the second Vanessa. And on Sunday, the measure was approved in a nationwide referendum.

The outcome went against the recent tide of right-wing populism and anti-immigrant sentiment in much of Western Europe. Just over 60 percent of votes were in favor, including majorities in 17 of the country’s 23 electoral cantons — a minimum of 12 are required to pass — despite a right-wing campaign that sought to stoke fears of Muslims infiltrating the country.

“We are quite surprised,” said Stefan Egli, a manager of Operation Libero, a politically independent group that campaigned in support of the initiative and organized the poster campaign featuring the two Vanessas, among others. Mr. Egli said he had thought the referendum would win the national popular vote, but he worried that more of the rural cantons would oppose the change.

Swiss law typically requires foreigners to be residents of the country for 12 years before applying for citizenship; after that they must undergo a series of tests and interviews to assess their suitability, and are judged by criteria that differ from one canton to another. Unlike the United States and some European countries, Switzerland does not grant automatic citizenship to children born on its soil.

The measure approved on Sunday will not change those basic rules, but will speed up and simplify the approval process, using uniform criteria, for foreigners under 25 whose parents and grandparents have permanent residence status in Switzerland. “These are people who are at home,” Simonetta Sommaruga, the federal justice minister, said in a statement explaining the government’s position on third-generation immigrants. “The only difference is they do not have a red (Swiss) passport.”

An assessment by Geneva University for the government’s department of migration found that just under 25,000 people could benefit from the changes. Most of them are Italian, it found, and nearly 80 percent are of European extraction.

Vanessa Seyffert, the second woman in the poster, will not be one of them; she is already deep in the process of applying the old way. She said she had taken part in the poster campaign to highlight the inequality facing young people who were brought up attending the same schools and speaking the same language but do not have the same rights. “The crucial thing for me is to be able to vote,” Ms. Seyffert said in an interview. “I just want to have a voice.”

Noncitizens make up one-quarter of Switzerland’s eight million residents, one of the highest proportions in Europe, and the continent’s refugee crisis has sharpened fears in the country of a dilution of national culture and character. Changes to the country’s restrictive immigration laws, even modest ones like the referendum on Sunday, tend to touch a nerve. Given the climate, proponents said they saw almost no chance of enacting broader changes, like automatic citizenship for third-generation immigrants, which was defeated in a 2004 referendum.

“We don’t see any reason whatsoever to make it easier,” said Luzi Stamm, a legislator from the right-wing People’s Party, which favors making controls on foreign workers and migrants even tighter. “The movement of people in the world has increased considerably,” he said. “You have an increased probability of problem-makers coming here.” To reinforce the point, the party mounted a poster campaign of its own, featuring a silhouette of a woman in a burqa and with the slogan “No to uncontrolled naturalization.”

Though the People’s Party has a long history of provocative posters and slogans playing on popular suspicion of outsiders, the current posters shocked many Swiss, who saw them as racist and irrelevant to the ballot measure.

“It’s quite systematic — they are really trying what Trump’s campaigns did, to go beyond the facts,” said Lukas Goldber, an analyst at Gfs.bern, a political and social research institute, referring to President Trump’s election campaign in the United States.

“Some elements were trying to see if it works in the Swiss system,” Mr. Goldber said. “It didn’t work at all.”(NYT)