France's choice of pro-EU Emmanuel Macron over eurosceptic Marine Le Pen has sparked euphoria in Brussels, but analysts warn his ambitions for profound change in the European Union will prove challenging.
Praise for Macron poured in from the EU capital, with Europe's top officials hailing his win as a much needed check to a populist wave that delivered Brexit and the election of Donald Trump in the United States.
"Happy that the French chose a European future," said European Commission President Jean-Claude Juncker, as EU observers noted triumphantly on Twitter that Macron had the EU anthem "Ode to Joy" play as he took the stage for his victory rally.
Outgoing president Francois Hollande said the result "confirms that a very large majority of our fellow citizens wanted to unite around the values of the Republic and show their attachment to the European Union."
Despite widespread doubts, analysts agreed that the sheer scale of his victory – Macron beat Le Pen with 66 percent of the vote – gave one of the EU's most powerful member states a small window to change the bloc.
This sweeping win is "a splendid opportunity to reform France and forge a deal with Germany and other European countries to strengthen the cohesion of the EU and the eurozone," said analyst Holger Schmieding of Berenberg Bank in Germany.
However, the results "also carry a stark warning [as] ... voters rebuked the traditional mainstream parties. Almost half of voters had fallen for anti-EU candidates in the first round," Schmieding added.
Macron, a former banker and economy minister, wants to strengthen the EU and the eurozone in deeper ways than any major leader in Europe has dared in a generation.
His promises include a plan to set up a separate budget for the 19 countries that use the common currency. He also proposes giving the eurozone its own parliament and finance minister.
"His reform programme aligns perfectly with the European framework (in Brussels)," said analyst Amandine Crespy at ULB university in Brussels.
Until now, ideas involving more Europe have been largely ignored as too idealistic when nationalism and euroscepticism were on the rise across the EU.
"Pushing through these reforms at EU level could prove politically difficult as other EU partners may want to focus on alternative priorities such as migration and security," said Robin Huguenot-Noel, policy analyst at the European Policy Centre.
Germany a crucial ally
The first and crucial step will be to get Germany, the bloc's most powerful member, onside.
To do that, Macron is banking on delivering to Germany what it has always wanted from France: meaningful pro-market reforms.
But Macron's willingness to placate Germany has led critics at home to portray him as the puppet of Chancellor Angela Merkel.
Germany's Chancellor Angela Merkel congratulated Macron on his "spectacular" election success, pledging to help France tackle unemployment and to work together to promote European stability.
"He carries the hopes of millions of French people, and of many people in Germany and the whole of Europe," Merkel told a news conference in Berlin on Monday. "He ran a courageous pro-European campaign, stands for openness to the world and is committed decisively to a social market economy."
Franco-German cooperation was a "cornerstone" of German foreign policy, she said, but added that Germany did not need to change its economic course in response to Macron's election victory.
Macron will get his first taste of the challenges ahead on Thursday when the European Commission delivers it economic forecasts for EU members.
The expectation is that France will once again be in the firing line for public overspending and in danger of facing penalties for not delivering on reforms.
Macron has pledged to do so in his first weeks in office but the proposed changes will likely face fury in France.
"Macron will need to brave some protests. But unlike Hollande before him, he now has the mandate to do so," said Schmieding.