The yes is the big favorite among the 4.3 million voters called to the polls, having progressed to more than 65% of voting intentions in the last poll published on Sunday.

But caution remains in order because of the expected high abstention, in a country used to saying “nej” (no) to referenda on Europe, the last in 2015.

“I believe with all my heart that we have to vote yes. When we have to fight for the security of Europe, we have to be more united with our neighbours”, said Prime Minister Mette Frederiksen during a final debate campaign television show on Sunday evening.

A member state since 1972, Denmark had fired the first cannon shot of Euroscepticism by rejecting the Maastricht Treaty by 50.7% in 1992, unheard of at the time.

To lift the blockage – which threatened the entry into force of the founding treaty throughout the European Union – Copenhagen had obtained a series of exceptions, called “opt outs” in European jargon, and the country finally said yes in a new ballot the following year.

Since then, Denmark has remained outside the euro – rejected by a referendum in 2000 – but also from European policy on home affairs and justice – again rejected by referendum in 2015 – as well as defence.

By virtue of this last exception, the Scandinavian country – a founding member of NATO – was thus unable to participate in any EU military mission.

Formerly marginal, the defense policy of the 27 has gained momentum in recent years, even if the ideas of a European army are still a foil for many capitals.

Otan and the EU

Two weeks after the invasion of Ukraine, the Danish Prime Minister had announced an agreement with most parties in Parliament to submit the end of the exception to a referendum, as well as significant military investments to overcome the bar of 2% of GDP desired by NATO.

Eleven parties out of 14 called for a yes vote, representing more than three-quarters of the seats in Parliament.

The two far-right eurosceptic formations of the Danish People’s Party (DF) and the New Conservatives, as well as the radical left formation of the Unity List, are campaigning for the no.

With the historic candidacy of Sweden and Finland for the Atlantic alliance and the Danish referendum, the three Nordic countries could soon combine European defense policy and participation in NATO.

Polling stations will be open from 8 a.m. to 8 p.m. local time (6 a.m. to 6 p.m. GMT). The results are expected late Wednesday evening, around 11:00 p.m. local time (9:00 p.m. GMT).

Autonomous territories of Denmark, neither Greenland – which is already outside the EU – nor the Faroe Islands are concerned by the ballot.