Pablo Iglesias, leader of Spain's anti-austerity Podemos party, at a news conference in Madrid. He cheered Sunday's “no” vote in Greece, saying on Twitter: “Today in Greece democracy won.” (Andrea Comas/Reuters)

When voters in Greece did the previously unthinkable and defied Europe’s political titans by spurning their bailout proposal, some of the loudest rejoicing came from well beyond the country’s borders.

Across the continent — from north to south, from the far right to the far left — parties that have rocketed to prominence with populist rhetoric celebrated what they saw as perhaps the most direct strike yet at the heart of the European order.

“Today in Greece democracy won,” Pablo Iglesias, leader of the radical leftist Spanish party Podemos, cheered on Twitter.

The result was a victory against “the oligarchy of the European Union,” declared Marine Le Pen, leader of France’s far-right National Front party.

Greeks overwhelmingly voted against a strict bailout package proposed by the European Union. Here is how that affects Greece and the United States. (The Washington Post)

The enthusiastic response from such unlikely bedfellows reflects the strange new politics of Europe, which have pitted mainstream parties against formerly fringe movements that, for different reasons, are determined to tear down the systems and ideologies that have governed the continent for decades.

Lately, the outsiders have been surging. And in Greece, they see the first true battleground in a much wider war — a potential beachhead that can ultimately help them achieve either Europe’s profound transformation or its undoing as an integrated union.

“There’s a general euphoria among the populist parties because a national government and its people have been able to stand up to the dictatorship and the bureaucracy of Brussels,” said Vincenzo Scarpetta, an analyst with the think tank Open Europe. “Greece has become a testing ground for the European project.”

But whether European populists gain or lose in the coming years may turn on the question of how the Greek crisis is settled.

The reasons for the populist challenges vary from country to country and from party to party. But they are all built on a shared sense that Europe has gone badly off track, whether through merciless economic policies that have widened the gap between rich and poor or through an overly permissive approach to immigration.

The parties also differ in their prescriptions. Some, such as Le Pen’s National Front, want to get rid of the European Union altogether and restore national supremacy, including tight border controls.

Others, such as Greece’s ruling Syriza and Spain’s Podemos, seek to fundamentally reshape the E.U. from within by overturning the dogma of austerity that took hold in the wake of the 2008 global financial crisis.

A tricky path forward

The broader challenge to the European status quo is one reason Greece’s fate in the coming days and weeks matters so much — not only to Greece but also to those, such as German Chancellor Angela Merkel, who see it as their responsibility to maintain the existing order.

It also explains why Merkel’s calculations are so tricky — and have become even more so in the aftermath of Sunday’s referendum in Greece.

When Syriza won national elections in January, it became the first radical leftist party in the E.U.’s history to take power. The party immediately threw down a gauntlet, demanding that Europe forgive a chunk of Greek debt and allow the new government to ease the strict austerity that had been implemented as a condition of the bailouts given to the country.

Merkel and her fellow European heavyweights have stood firm, not wanting to allow Syriza a victory that could inspire similar movements in other debt-ridden nations.

That risk may be especially pronounced now that the Greek public has so resolutely backed its government and spurned European leaders who had been hoping that a yes vote could be a catalyst for regime change in Athens.

Since the vote, German and other European officials have shown no new leniency. But Scarpetta said that although they may not want to encourage other leftist parties by giving in to Syriza, they will still seek to avoid the unraveling of the 19-member euro zone.

“Merkel’s probably not keen to be remembered as the chancellor who let Greece go and, therefore, burst the myth of the irreversibility of the single currency,” he said.

Podemos and other leftist parties in southern Europe sent emissaries to Athens on Sunday to express solidarity with Syriza, and they ended up partying into the wee hours alongside thousands of Greeks.

On Monday, Iglesias, Pod­emos’s ponytailed, 36-year-old leader, said the results had emboldened the anti-austerity camp across Europe.

“It’s a very clear message,” he told Spanish radio station Cadena Ser. “The citizens of Greece have said that austerity isn’t the way to end the economic crisis.”

But he was also cautious about drawing too close a parallel between his country, which has been modestly recovering under a conservative-led government, and the one that’s on the cusp of being ejected from the euro zone.

“We have a great friendship with Syriza, but, luckily, Spain is not Greece,” he said.

That sort of restraint is warranted, said German Marshall Fund fellow Timo Lochocki. If Greece exits the euro zone and its economy goes into free fall, he said, it will turn Sunday’s referendum into “a Pyrrhic victory by epic standards.”

And that, he said, will blunt the appeal not only of far-left parties such as Podemos but also of far-right parties, because it will allow mainstream governments to claim that they are resisting a giveaway to Greece.

“They can say, ‘We’re standing up for your interests,’ ” he said. “Greece’s government isn’t the only one in Europe that’s been democratically elected.”

Populist political players

Of the other far-left parties in Europe — which are far stronger in southern Europe than in the north — Podemos has the best chance of taking a share of power. Spain is due to vote toward the end of the year, and although the party is not expected to win, it could emerge as a kingmaker.

Populist parties on the right have become critical players in Danish and Finnish politics this year after elections in which they swept up a larger share of the vote than ever before.

In Britain, too, populism is on the rise. The anti-austerity Scottish National Party trounced its opposition in May elections, and the anti-immigration U.K. Independence Party won the third-highest share of the vote across Britain.

The governing Conservative Party is hardly populist. But Prime Minister David Cameron’s ambition to win reforms for the E.U. ahead of a referendum on Britain’s membership in the 28-member body could get an indirect boost from Greece.

Scarpetta said that as the crisis escalates, Cameron may have an easier time convincing his European counterparts that the union needs to change its ways.

Perhaps that is why, even as Cameron called for Greeks to vote yes, London Mayor Boris Johnson, a fellow Conservative, did little to conceal his delight with the outcome.

“EU bluff called,” Johnson tweeted. “EU political class told Greece to vote yes — and Greeks told them to bog off.”

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