With France’s presidential election on Sunday being so completely unpredictable, the danger of Marine Le Pen is real – but so is the danger of another brand of polarising, radical and destructive populism. It is found on the far left, with the ascendancy of Jean-Luc Mélenchon.

Some progressives have taken to describing the 65-year-old former senator and former junior Socialist minister as the new embodiment of a rejuvenation of the left. That Mélenchon has managed to gain in the polls to the point of perhaps being able to reach the presidential run-off is certainly no small feat. But to believe that his campaign stands for an attractive, socially minded and more democratic or alternative Europe is delusional.

Mélenchon is essentially a nationalist, despite his internationalist credo. And his sympathies for autocratic strongmen such as Vladimir Putin or Hugo Chávez cannot be easily swept aside, as if these were just missteps in an otherwise promising platform. If you believe that the European project must be salvaged and improved rather than dismantled, Mélenchon really cannot be your man. Not if you look closely.

To be sure, he’s having a good run. Unfamiliarity helps. Many outside France – and within it, notably among young people – have only recently discovered him. He’s managed to capitalise on some of the rage that animates much of the electorate: he’s apparently even stealing votes from Le Pen. The French are exhausted by decades of high unemployment, they’re deeply distrustful of the political class, and they’re worried about an unpredictable international environment.

Mélenchon is a talented orator. His fiery rhetoric in speeches and savvy, quickfire remarks in recent television debates have helped his numbers surge. One of his slogans is “degagisme”, which can translate as “kick them out” – targeting the rest of the political class. He likes to quote Maximilien Robespierre and Victor Hugo. He casts himself as a hero of the people (“les gens”), a single, homogeneous entity, set against the establishment. His frequent references to the revolution of 1789, to French socialist hero Jean Jaurès and to three-times prime minister Léon Blum have buoyed voters yearning for lyricism, or a dose of nostalgia. And there is no doubt that Mélenchon wants Le Pen to be defeated.

‘Jean-Luc Mélenchon casts himself as a hero of the people, a single, homogeneous entity, set against the establishment. But there is more to him than a crusade for social justice.’ Photograph: Charles Platiau/Reuters

But there is more to him than a crusade for social justice. Consider his anti-German narrative. In a tense country like today’s France, old antagonisms can quickly be reactivated. In his 2015 book Bismarck’s Herring (The German Poison), Mélenchon wrote that “Germany is again a danger”, its “imperialism” is “returning”, and the EU is its “new empire”.

He’s described Germans as “grumbling Teutons” who seek to “deport” their old people to eastern Europe or Thailand. And he’s written that German “expansionism” was at work in the country’s 1990 reunification – an “annexation” of East Germany, in his words. That in itself is no small rewriting of history, and no small denial of a people’s freely expressed will after the fall of communism.

His criticism of Angela Merkel’s eurozone policies goes far beyond the economic. It peddles nationalistic, if not bigoted, hatreds. He may have tried to soften that impression by saying he wants “the peoples of Europe” to revolt against their governments – and not start to fight among themselves. But he has hardly backtracked on any of his earlier statements. Much of this echoes and amplifies Le Pen’s rhetoric, rather than helping to combat it.

‘Mélenchon’s criticism of Angela Merkel’s eurozone policies echoes and amplifies the rhetoric of Marine Le Pen (left) rather than helping to combat it.’ Photograph: Claude Paris/AP

Which brings us back to Putin: a hero of Le Pen’s Front National and a constant focus of Merkel’s concerns over the future of the continent. Mélenchon has no particular liking for Putin’s autocracy (although in 2015 he preferred to criticise Boris Nemtsov, an opposition figure assassinated that year in Moscow, rather than blame Putin for anything). But what is most striking about the far-left leader is how he’s systematically refrained from ascribing any responsibility to Russia over the war in Ukraine and the annexation of Crimea, not to mention the killing fields of Syria. Only the west is ever held guilty for anything. This hasn’t changed, even after chemical weapons were used this month and Russia vetoed a UN-sponsored investigation into the crime.

Mélenchon’s rallying cry of “peace” on Earth sounds laudable, but his success would have severe consequences for Europe. Pulling France out of Nato and out of EU treaties, which he wants, would unravel Europe’s architecture. It would mean a leap into the unknown, not unlike that advocated by Le Pen. His radical economic policies would kill any hope of reforming eurozone governance. Meanwhile, his vision of international relations – in which Russia’s revisionism over European borders and the Syrian dictator’s mass killing of his own citizens hardly get a mention, whereas western democracies are constantly critiqued – smacks of moral confusion, and much worse.

Nor is Mélenchon as refugee-friendly as some would like to think. He’s suggested that he’d prefer to see “10,000 doctors” settle in France rather than a wave of huddled masses. “I’ve never been in favour of freedom of arrival,” he’s said. He’s also on record accusing some foreign workers of “stealing their bread” from French workers. There is much more of Italy’s firebrand populist Beppe Grillo about him than Spain’s Podemos.

As the rightwing press dubs him France’s “would-be Chávez”, his charisma protects him. But charisma cannot address so many worrying traits. Hankering for a “citizens’ uprising” and questioning the institutions is one thing, but Mélenchon’s politics arrive laden with baggage that can’t easily be discarded.

Victor Hugo’s observation that misery brings people to revolution, and revolution in turn brings them back to it, is well worth remembering as France prepares to vote. A choice between Le Pen and Mélenchon in the presidential run-off on 7 May would likely lead to record low turnout and unprecedented gains for the far right. Those who admire from afar should keep that in mind. And those tempted to follow Mélenchon’s route towards the crumbling of the “old order” need to be careful what they wish for.