Swiss voters backed a measure to legalize same-sex marriage by a large margin on Sunday.

Nearly two-thirds of voters supported the measure in a national referendum, the Associated Press reported, and it won a majority in each of Switzerland’s 26 cantons. The measure will also allow same-sex couples to adopt unrelated children and married lesbian couples to access sperm donation, according to the BBC.

Approval, a victory for gay rights advocates after a years-long campaign, puts Switzerland in line with many countries in Western Europe.

The country of 8.5 million tends to lean more conservative than its neighbors on social issues. Switzerland has permitted same-sex civil partnerships since 2007, but conservative political parties and church groups had argued that same-sex marriage would undermine the traditional family headed by one man and one woman.

Switzerland agreed to legalize civil marriage and the right to adopt children for same-sex couples by a nearly two-thirds majority in a referendum on Sept. 26. (Reuters)

“It is a historic day for Switzerland, a historic day when it comes to equality for same-sex couples, and it is also an important day for the whole LGBT community,” Jan Miller of the “yes” campaign committee told Agence France-Presse. Supporters celebrated Sunday in Bern, the capital, with kisses and rainbow-colored cake. Drag artist Mona Gamie sang Edith Piaf’s “Hymn to Love.”

Amnesty International called opening civil marriage to same-sex couples a “milestone for equality,” Reuters reported.

The measure will also help same-sex spouses who are foreign nationals to acquire Swiss citizenship, advocates said. Supporters say it could take months before same-sex couples can get married, though, because of administrative and legal procedures, according to the Associated Press.

Opinion polls leading up to the referendum indicated that the Swiss population supported same-sex marriage, and the country’s parliament passed a law last year to allow same-sex couples to wed.

But that legislation prompted a strong backlash from opponents, who gathered enough signatures to force a binding referendum on the issue under Switzerland’s system of direct democracy.

The campaign leading up to Sunday’s vote was marked by allegations of unfair tactics, including the ripping down of posters, opponents deluging LGBTQ hotlines with complaints and other efforts to suppress opposing views, according to the Associated Press.

Monika Rüegger of the right-wing Swiss People’s Party, who campaigned against the “Marriage for All” measure, told Reuters after the polls closed that “children and fathers are the losers here.”

But for many couples in Switzerland, Sunday’s vote seemed to herald new possibilities and societal acceptance.

“I think it’s like a strong signal that would actually be so great for all the young queer people who might be struggling still, with coming out or with their sexual orientation,” Roman Heggli of Swiss LGBTQ group Pink Cross told the LGBTQ news outlet PinkNews ahead of the vote.

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