Former US president says centrist, who faces far-right Marine Le Pen in runoff, appeals to hopes not fears

Barack Obama has made a last-minute intervention in the French presidential election in support of Emmanuel Macron, saying “the success of France matters to the entire world”.

Macron, a centrist, faces Marine Le Pen of the far-right Front National in a runoff vote on Sunday. Polls put him 20 points ahead.

The former US president said he had chosen to declare his support, in a video tweeted by Macron on Thursday afternoon, because of the importance of the election.

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“I’m not planning to get involved in many elections now that I don’t have to run for office but the French election is very important to the future of France and the values that we care so much about,” he said.

Obama said he supported Macron because he appealed to “people’s hopes and not their fears” and ended his message with the words “Vive la France.”

Before leaving the White House, Obama said he would intervene in public life again when “our core values may be at stake”.

Charles Kupchan, a former special assistant on Europe in the Obama White House, said he thought Europe’s fate involved those core values. “President Obama was very concerned about the political trajectory of the European Union, particularly after the refugee crisis of 2015. He became quite seized with helping to rebuild self-confidence in liberal values and practices,” said Kupchan, now a professor of international affairs at Georgetown University.

Obama flew to London in April 2016 to urge Britons to “stick together” with the EU, but it failed to fend off Brexit. “One will never know whether the visit to London was a help or in the end did more harm than good,” Kupchan said. “But if we had to do it again, I would recommend the same thing. We should be speaking out.”

Philip Gordon, who was assistant secretary of state for Europe in the Obama administration, said: “It’s not surprising [Obama] has done this. Macron represents everything he is for and Le Pen everything he is against.”

Who are Macron and Le Pen and what do they stand for? • Emmanuel Macron and Marine Le Pen are the two candidates in the French presidential election runoff on Sunday 7 May. • Macron, 39, is the head of the En Marche! (Forward) movement. He defines himself as an outsider, 'of the left' and progressive on social issues, but economically liberal and pro-business. The former investment banker, who served as a Socialist economy minister, also wants closer cooperation on European issues. • Le Pen, 48, is the candidate of the far-right Front National party. A lawyer by training, she has attempted to detoxify the party. She wants to clamp down on immigration, slash crime, eradicate Islamism, and pull France out of Europe. Le Pen is in favour of 'economic nationalism' and social policies that favour French people.

However, Gordon, now a senior fellow at the Council on Foreign Relations, raised the possibility the intervention could backfire. “Macron obviously thinks it will help. Obama remains very popular in France,” he said. “But I do worry it could motivate Le Pen voters who are anti-elite or anti-American or even racist, so that it hurts Macron more than it helps.”

The intervention comes a day after Macron and Le Pen met in a bruising televised debate that French media widely judged the frontrunner to have won. The two traded personal insults and clashed over how to fix the country’s sluggish economy and fight terrorism.

In the two-and-a-half-hour slanging match that featured more invective than any other debate in French presidential history, Macron branded Le Pen an ill-informed, corrupt, dangerously nationalistic and “hate-filled” liar who “fed off France’s misery” and would bring “civil war” to France.

She in turn called the former economy minister an arrogant, spoilt, cold-eyed “smirking banker” who was colluding with Islamists, complacent on terrorism and intent on “butchering France” in favour of “big economic interests”.

Both accused the other of taking French people for imbeciles. At one point, after a long attack in which he accuse Le Pen of lying to the French public, Macron snapped: “I’m sorry, Madame Le Pen, France deserves better than you.”

Viewing figures showed 16.5 million people watched the debate and snap polling by Elabe for BFM television found a clear majority felt the centrist candidate had been the most convincing.

French media criticised Le Pen for her “permanent aggression”. Libération accused Le Pen of “multiplying attacks and provocations … and thus avoiding any serious debate,” while Ruth Elkrief, political editor for BFMTV, declared it “not worthy of a presidential election campaign”. Even normally sympathetic publications found her “unconvincing”.

Aides to Macron said on Thursday he had brought a defamation complaint against Le Pen after she said during the debate: “I hope that we will not find out that you have an offshore account in the Bahamas.”

Judicial sources told Agence France-Presse that Paris prosecutors had opened an investigation. “We will not hesitate to prosecute for defamation anyone who repeats this false information,” an aide to Macron said.

Le Pen’s comments were an apparent reference to a set of clearly forged documents circulating on the internet that linked Macron to a Caribbean bank.

Macron characterised the insinuations as “fake news and lies” from “sites, some of which were linked to Russian interests”. He told a radio interviewer that he never held a bank account “in any tax haven whatsoever”.

Le Pen said on Thursday she was not accusing Macron of having a secret offshore account. “Not at all. If I wanted to do so I would have done it yesterday. I’ve just asked him the question. If I had proof, I would have claimed it yesterday,” she told BMFTV.

Macron, a former economy minister who has never stood for election before, set up his “neither right nor left” En Marche! (On the Move) movement a year ago.

Le Pen, who took over the far-right Front National from her father six years ago, has never held a ministerial or French parliament post. She and Macron both claimed to be anti-establishment candidates who aimed to reinvent French politics.

Le Pen said on Thursday she was not accusing Macron of having a secret offshore account. “Not at all. If I wanted to do so I would have done it yesterday. I’ve just asked him the question. If I had proof, I would have claimed it yesterday,” she told BMFTV.