Switzerland is voting Sunday in a referendum on limiting immigration from the European Union and some other domestic measures.
If the freedom-of-movement proposal by the populist Swiss People's Party were to pass, it would give preferential access to jobs, social protection and benefits to Swiss citizens over those from the 27 countries of the EU, of which Switzerland is not a member.
It also could lead to reciprocal disadvantages to Swiss citizens wanting to live or work in any of the EU member countries.
Approval of the measure could endanger trade relations with the EU, which is Switzerland's biggest trading partner.
About 1.4 million EU citizens live in Switzerland, a country of roughly 8.2 million, while some 500,000 Swiss live in EU member countries.
In a similar referendum in 2014, the Swiss voted for limiting the ability of EU citizens to live and work in Switzerland but lawmakers did not allow its full implementation, which prompted the nationalist People's Party to return the proposal to the ballot this year.
Recent polls show there is now less support in Switzerland to limit free movement with the EU.