Ljubljana - Slovenians vote Sunday in a referendum on whether to allow the largely Catholic EU member and former Yugoslav republic to become the first ex-communist country in Europe to allow same-sex marriage.
In March, parliament approved legislation redefining marriage in Slovenia as a "union of two" instead of being a "union of a man and a woman", giving equal rights including over the adoption of children.
But opponents immediately launched a campaign to reverse the changes, meaning they never entered into force. No gay or lesbian couples were able to actually tie the knot.
A group calling itself "Children Are At Stake" managed to gather the necessary 40,000 signatures to secure a referendum.
A heated debate ahead of the vote has even seen Pope Francis wade in, urging Slovenian politicians and people "to support the family, a structural reference point for the life of society".
The latest poll released by state television on Friday gave the "No" vote -- against gay marriage -- 55.5 percent support, with projected turnout of 46 percent.
In order for the result to be valid, the winning side must include at least 20 percent of eligible voters. Other surveys have indicated a tighter result, however.
If the "No" vote prevails, then the civil code will be changed back, although existing legislation allowing registered civil partnerships -- but not adoption of children -- will remain in force.
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This is not the first such referendum on the subject, with Slovenian voters having rejected gay marriage in an earlier plebiscite in 2012, although turnout was low.
Preliminary results are expected from 9:00 pm (1900 GMT).
Slovenia has long been ahead of its peers, joining the EU back in 2004 -- nine years before neighbour Croatia -- and the eurozone in 2007 as its first ex-communist member, but its society retains a strong traditionalist streak.
President Borut Pahor and Prime Minister Miro Cerar's ruling Modern Centre Party (SMC) support the "Yes" camp, saying gay marriage would eliminate discrimination and grant equal rights to all citizens in the two-million-strong country.
"At this referendum we're deciding what kind of Slovenia we want to live in," Nika Kovac, a coordinator from the "Cas je Za" (It's time For a Yes) campaign group, told AFP.
"We'll decide whether we want to join the developed world."
Janez Jansa, the former centre-right prime minister from the opposition Slovenian Democratic Party (SDS), strongly disagreed.
"Erasing the gender from the marriage (definition) gives ground to human rights' violations against our most precious -- our children," Jansa said.