Postal voting has already begun on the government's attempt to prolong an accord on free movement of labour - which also provides some 400,000 Swiss migrants unrestricted access to jobs in the European Union - and to extend it to the bloc's most recent members, Bulgaria and Romania.
Campaigning has pitted non-member Switzerland's economic interests against traditional popular fears about immigration and the neutral Alpine nation's prized independence. More than one million of the country's 1.62 million foreign residents come from the EU and western Europe. Their number has surged by nearly 200,000 since limits on employing EU citizens were gradually lifted from 2002, helping to fuel a Swiss economic boom until last year.
Swiss President and Finance Minister Hans-Rudolf Merz recently warned that a 'no' vote could topple the pile of bilateral accords, including transport, education and agriculture, that underpin an often tetchy relationship with the EU. Those agreements also ease an estimated one billion Swiss francs a day in economic exchanges with Switzerland's top trade partner, according to official data. "Our country is opposed to membership, but we recognise that we wouldn't be able to go it alone without ending up in complete isolation, and we couldn't afford that," Merz said.
While the latest move is actively backed by the bulk of the Swiss political, business and social establishment, popular support has been timid. In the last opinion poll released by Swiss state television on January 28, just 50 per cent of those polled supported the motion. However, 43 per cent rejected it and seven per cent were undecided, marking a marginal gain for opponents in a month and only a slender advantage for pro-Europeans. That contrasted with the 67 per cent of Swiss voters who approved free movement of labour in a referendum nine years ago and a clear majority when it was last expanded to match the enlarged EU in 2005.
Opponents in the hard-right Swiss People's Party (SVP) - the country's largest political group - appear to have captured the mood of many voters by whipping up fears about Bulgarian and Romanian immigrants. The SVP's campaign poster depicts ravenous crows pecking at Switzerland, while the party calls Bulgaria and Romania as the ‘Europe's third world’. "We did favour the prolongation, but we oppose the extension to these two countries, because we don't believe they're ready to integrate in the EU," SVP Vice President Yvan Perrin told Swiss television TSR.
The results of the referendum are expected in the early afternoon as polling stations close at noon (1100 GMT).