Dutch voters will decide on Wednesday whether spy agencies should have the power to install bulk taps on Internet traffic, just as news of Facebook's 50 million user profile leak returns digital privacy issues to the fore.
The referendum is non-binding, but Prime Minister Mark Rutte said in a televised debate on the eve of the vote his government would take the outcome seriously.
"It's not that our country is unsafe, it's that this law will make it safer," he said, advocating a "Yes" vote.
Dubbed the "trawling law" by opponents, the legislation would let spy agencies install taps targeting an entire geographic region or avenue of communication, store information for up to three years, and share it with allied spy agencies.
Digital rights group Bits of Freedom, which advises a "No" vote, says the law isn't all bad but will lead to privacy violations and should be reconsidered.
The Netherlands' Council of State, which vets new laws, has said the scope of data collection it allows is disproportionate, and that it may violate privacy provisions of the European Convention on Human Rights.
"Yes" advocates say that British, French and American intelligence agencies already have greater powers and the Dutch are being left behind.
"Look at what Facebook, Google, Twitter and Tinder know about you, and consider whether you're worried about the right things," the head of national intelligence agency Rob Bertholee said in a recent interview with De Telegraaf newspaper.
Opinion polls show Wednesday's vote is too close to call.
The anti-establishment sentiment that led to Dutch "No" votes in the 2006 referendum on a European constitution and the 2016 referendum on a EU association treaty with Ukraine has eased. The economy is booming and Rutte's new government took power only in October.
The Dutch are voting separately on Wednesday in municipal elections that are expected to reflect a splintering of the country's far right.
The Freedom Party of Geert Wilders, known for apocalyptic anti-Islam warnings, is expected to lose ground to the upstart Forum for Democracy, whose leader Thierry Baudet has instead emphasized Dutch nationalism and cultural values. Both oppose immigration.
Voting stations close at 9pm, with the exit poll published by national broadcaster NOS expected within a half an hour.