Geneva - Swiss voters on Sunday approved a measure to make it easier for third-generation immigrants to become citizens, crushing rightwing nationalists who had stoked fears about granting nationality to more Muslims. According to final official results, the "Yes" camp claimed 60% support and a victory in 19 of Switzerland's 26 cantons, meeting the two criteria needed for a win.The government as well as most lawmakers and political parties supported the proposal.Acquired residencyUnder it, the grandchildren of immigrants will be able to skip several steps in the lengthy process of securing a Swiss passport, although approval of their citizenship will still not be automatic.The rightwing Swiss Peoples Party (SVP), the largest party in Switzerland's parliament, fought against the measure by putting Islam and national identity at the centre of the debate.Reacting to the defeat, SVP lawmaker Jean-Luc Addor said his side was "alone against everyone in this campaign. "The problem of Islam, I'm afraid...it will catch up with us in a few years," he said. According to a migration department study, less than 25 000 people in the country of about eight million currently qualify as third-generation immigrants, a definition meaning they have at least one grandparent who was born in Switzerland or acquired residency.Nearly 60% of that group are Italians, followed by those with origins in the Balkans and Turkey.During the campaign, Addor warned that third-generation immigrants in Switzerland will increasingly be people "from sub-Saharan Africa, the Horn of Africa, Syria or Afghanistan."Democracy systemThe "No" camp faced heavy criticism over a widely-distributed poster showing a woman staring out from under a black niqab with a tagline urging voters to reject "uncontrolled citizenship".The SVP was not officially responsible for the poster.It was commissioned by the Committee Against Facilitated Citizenship, which has several SVP members and was co-chaired by Addor.