The shock victory of Geert Wilders's far-right eurosceptic party in Dutch elections sent a political tremor through Brussels, seven months ahead of crucial EU elections.
Despite Wilders's promise to hold a "Nexit" referendum, pro-European parties do not yet fear that the Netherlands is going to follow Britain in quitting the European Union.
But his first place finish in a core member of the union is a reminder that populist parties are expected to grow in strength in next year's European Parliament elections.
"The European Union is in danger of death from within and without," socialist MEP Raphael Glucksmann said in an interview with the France 2 network, warning that Russia's President Vladimir Putin would be celebrating Wilders's triumph.
"Elections take place at regular intervals in the member states. And this does not, per se, put in doubt in any way the membership of any country to the European Union," European Commission spokesman Eric Mamer said.
"We continue to count on the Netherlands strong participation in in the European Union, obviously," he told reporters.
Wilders's PVV may not be able to build a coalition to make him prime minister so he can join the other 26 EU members at their summits.
And his hardline plans to expel immigrants would be unlikely to survive legal challenges in the Dutch or European courts.
But Europe's support for Ukraine, grand plans to fight climate change and efforts to build a joint strategic position in the face of crises like the Gaza war could be endangered.
'Bring on June 2024'
European elections to be held in June will be a new test of Wilders's popularity.
With 17 million people, The Netherlands is the seventh most populous EU country and its MEPs -- along with right-wingers from countries like Poland, Italy, France and Hungary -- could form a powerful group.
"We can expect at least a consolidation of right-wing populists, even an increase in their number of seats in the European Parliament, said Nathalie Brack of Brussels Free University.
The PVV does not have any seats in the current parliament, but next year they could join the National Rally (RN) of France's Marine Le Pen and Germany's AFD in the assembly's Identity and Democracy group.
That is what the European far-right hopes for.
"Bring on June 2024!" exclaimed French RN MEP Jordan Bardella, in a social media post hailing Wilders's win as a "beautiful defeat" for supporters of immigration and Islamism.
The larger ECR group of eurosceptic parties, currently dominated by Poland's PiS and Spain's Vox, could also benefit from a populist surge, the political scientist Brack told AFP.
The ECR already has 67 seats and could pass the Greens, currently on 72, thanks to what she called "a generalised discontent" with traditional centre parties.
"There is even the chance that ECR becomes the third group in parliament if, for example, the liberals are punished at the polls," she said.
Climate champion sidelined
Traditionally, European legislation moves forward backed by a broad coalition of the pro-European centre right and centre left.
If such groups did not have a working majority, law-making could grind to a halt and the most ambitious plans of supporters of the "ever closer union" would be halted or reversed.
Far-right gains are not the European centre's only worry, however. The Netherlands' elections were a setback for one of its champions: Dutch social democrat leader Frans Timmermans.
Until recently a vice-president of the European Commission and architect of the the EU's plan to reach net zero emissions by 2050, Timmermans returned home to lead a left-green coalition in the Dutch campaign.
Now, with his group coming in behind the far-right, he is in a weak position to negotiate a role in the next governing coalition.