A proposal to ban the construction of minarets appears to be winning support, but is still some way short of a majority, according to the latest opinion poll.
Two weeks ahead of the nationwide vote at the end of November, 53 per cent of respondents said they reject the rightwing initiative, while 37 per cent said they approve the ban. A further ten per cent were still undecided.
The survey was carried out by gfs.berne - a leading research and polling institute - on behalf of the Swiss Broadcasting Corporation, swissinfo's parent company.
"The percentage of supporters is on the increase, which is untypical for a people's initiative. But the no side still has an edge," said the head of institute, Claude Longchamp.
The survey, which was conducted among more than 1,200 citizens across the country between November 9 and 14, found that the ban appears to be popular among supporters of rightwing parties, residents of rural areas and towns in the German-speaking part of the country, as well as among less qualified people.
"This is a pattern known from other campaigns which target the fears and concerns of the population," Longchamp added.
However, he was surprised by evidence that the divisive initiative has gained ground among citizens without clear party affiliation – this group accounts for up to 30 per cent of respondents - compared with a first poll in October.
Islam's alleged pretension to power, symbolised by minarets, is the argument which has the most popular appeal, according to researchers.
Human right concerns were frequently quoted by opponents of a ban, while potential damage to Switzerland's international relations also appeared to sway opinion their way.
There was clearly no dominant argument on the no side, and opponents of a ban had been wrongfooted by the direction the pro campaign took, according to Longchamp.
"It appears they underestimated the importance of a broad discussion about Islam in our society. It was clearly not sufficient to reject the anti-minaret posters," he said.
"The rightwing cleverly extended the debate to issues including integration of Muslims and their faith. These concerns have never been addressed in a nationwide context before."
He says opponents have so far failed to identify a political weakness in the initiative.
Based on the findings of the latest poll, and given the increasing support for outlawing new minarets, experts conclude that the ballot is more open than after the first survey a month ago.
"The outcome of the ballot is uncertain, but the approval rate for a ban will most likely be below the 50 per cent threshold," Longchamp said.
He said it was not possible to forecast the result on November 29, but the poll gave an indication of the mood among citizens two weeks before the vote.
Longchamp also pointed out that it is crucial to consider the focus of polls and the methods used.
A survey by the MIS market research institute earlier this month found opponents of minarets in Switzerland ahead of supporters.
The poll included people who are not eligible to vote and did not cover the Italian-speaking region of the country. The gfs.berne institute survey claims to be nationwide and to have been conducted only among potential voters.
Urs Geiser, swissinfo.ch
Yes to minaret ban: 37% (+3%)
No: 53% (unchanged)
Undecided: 10% (-3%).
Expected turnout 50% (+6%).
1,213 people took part in the survey.
The margin of error was 3%.
Three issues will come to a nationwide vote on November 29.
A ban on the construction of minarets is a proposal launched by members of the rightwing Swiss People's Party and a small religious party.
A broad coalition of pacifist groups and centre-left parties forced a ballot on a proposed ban on the export of weapons and other war material.
Voters will also have the final say on a constitutional amendment to use revenue from a fuel tax on domestic flights for aviation safety and environmental measures instead of road projects.