The web platform was named for a revered French populist philosopher and created by an Italian internet entrepreneur to transform common grievances into proposals and activists into political candidates.
When Italy's deputy prime minister offered the populist 5-Star Movement's Rousseau platform to France's "yellow vest" protesters, he took a step too far for French President Emmanuel Macron. The president recalled France's ambassador to Italy for a week, in the sharpest diplomatic dispute between the two allies since World War II.
The sharing of the Rousseau technology marks the most brazen attempt to date to internationalize Europe's populist movements. It is a harbinger of the upcoming European Parliament elections in May, in which populist Euro-skeptics are poised to win an unprecedented one-third of the seats, under current projections. This could well complete the collapse of the mainstream, which up to now has held the largest voting bloc in Parliament.
However, the elections will also be a test of how far populist parties, which tend to be virulently nationalistic, can unite over countries and across the political spectrum. In Italy alone, the two populist ruling parties, the 5-Star movement and the League, compete at least as much as they cooperate.
"These parties are against Europe, but they are using Europe and the pan-European space to create a political debate," said Alberto Alemanno, an Italian analyst.
At their most basic level, populists on both the right and the left pit the common people against the elite, the entrenched political class.
Technology has helped them advance. The 5-Star Movement used the Rousseau portal to let activists click their way to choosing candidates and policies, much as Spain's Podemos used Reddit to energize online debate beginning five years ago and still uses online referendums. The populist yellow vests have yet to come up with a common online space, with proliferating Facebook groups and YouTube channels and no clear demands.
If ideology and organization trump geography, populist parties in Europe could form a bloc capable of weakening or even paralyzing the legislature, if projections released this week by the parliament hold.
"We must reject the financiers who see themselves as demigods, reject the Brussels bureaucrats representing their interests; and reject the fake civil society activists," Hungarian President Viktor Orban said in his state of the nation address this week.
On Friday, 5-Star leader Luigi Di Maio announced a new grouping of populist movements from across Europe, bringing together a far-right Polish party led by a former rock musician and a free-market Finnish party founded by a businessman-turned-reality TV star. Notably absent were nationalists, leaving open the question of how much sway the new alliance could have without expanding further.
Getting the far-left France Unbowed to vote in tandem with Orban's far-right Fidesz party seems a big hurdle. Italy's government, split between the two populist groups, is largely an unhappy marriage of convenience, and the 5-Star Movement and the League diverge at least as much as they ally.
But among the yellow vests, known as "gilets jaunes," ultra-right and ultra-left have marched together in hopes of bringing down the government.
"Here is the beauty of it: They are both the left and the right. It is a populist thing," political strategist Steve Bannon told France's l'Express magazine in an interview published just after Macron recalled the ambassador.
Bannon created a foundation in Brussels to strike at the heart of the European Union. Europe's populist far-right politicians — France's Marine Le Pen, Hungary's Orban, Italy's Matteo Salvini — haven't exactly embraced him, but nor have they pushed away the American many credit with propelling Donald Trump to the White House. He's been largely ignored by the populist far-left.
The European Parliament elections are actually a four-day series of national elections held across Europe that decide the makeup of the legislature. Members make Europe-wide law, decide international agreements, and — crucially — can censure EU countries for violating core values such as an independent judiciary and upholding the rights of minorities and migrants.
But even if they can unite on the issues that brought them to power, the anti-European populists may run into trouble with voters.
Across the board, trust in the European Union is higher than trust in national governments, according to the latest Eurobarometer poll taken in November 2018 — just as the yellow vest protests were taking root. The poll found 42 percent of Europeans trusted the EU, compared with 35 percent who trusted their own national governments or parliaments.
So even as Orban and Italy's populists position themselves squarely against Macron, they are keenly aware that their own citizens have little desire to overthrow the EU, although they list immigration as their prime concern. And Macron himself is something of an upstart — he vanquished France's two mainstream parties in the first round of the 2017 presidential elections and Le Pen in the second. Those two centrist mainstream parties, the Socialists and the Republicans, have since collapsed in France and are widely expected to do the same in the upcoming elections.
However, voters may also use the European Parliament vote to protest. Under current projections, the far-left and far-right are set to gain at the expense of the mainstream.
"Those voters who vote for the more radical parties just to express their frustration with Europe, they face a risk of voting for solutions that they wouldn't normally agree to," said Pawel Zerka, one of the authors of a study last week by the pro-EU European Council for Foreign Relations that said euroskeptics stand to gain the most.
Even some who are pro-EU do not think an alliance among euroskeptic populists is necessarily bad for the parliament. For Alemanno, the Italian analyst based in Paris whose last name translates loosely as "the German," it's ironic proof that the European idea is strong and durable, as populists come together in a European union of their own.
"In a way, I look at the yellow vests from an Italian perspective. I see the 5-Star Movement 10 years ago," he said.
The kind of interference that Macron found so intolerable from 5-Star will both become more common and even welcome, he said. In the short term, he added, the parliament and by extension the European Union may well be nearly ungovernable.
Le Pen has already shifted away from her longstanding position of abandoning the European Union and the euro. She renamed the nationalist party founded by her father, and Bannon made a surprise appearance at a major rally last year. And, she says, her brand of populist nationalism is no longer the exception.
"We can legitimately envision today to change Europe from inside, to modify the very nature of the European Union," she said, "because we consider ourselves powerful enough."