Marine Le Pen’s far-right Front National party has never been closer to power. That is not to say she will be elected president in May. When in 1962 Charles de Gaulle introduced direct universal suffrage for the presidential election, he cushioned it with a two-round voting system in which a 50% majority is required in the runoff. Le Pen seems set to pass the first hurdle, but not the second. In that case, the biggest danger lies not so much in her entering the Elysée Palace, but in her party becoming the largest opposition force in the National Assembly after the parliamentary elections in June. But don’t be mistaken, a worst-case scenario is possible.

The fact is, the taboo of a far-right presidency no longer holds in France. Low turnout in the runoff, combined with political polarisation, more scandals or, even worse, outbreaks of violence, could make a Le Pen win possible.

Looking at French politics with the Brexit and Trump campaigns in mind is enough to cause a shudder. Remember that in Britain a lot of those who wanted to remain weren’t very excited, while the passionate voices belonged to those who wanted to leave. Xenophobic populists were allowed to thrive in Britain and the US because mainstream parties (the Tories, the Republicans) provided them with a sufficient amount of complacency, if not complicity. The French far right is buoyed by similar factors. It knows that – as Gramsci put it – the battle of political ideas is waged in the cultural sphere as a whole.

Politics is not just fought in institutions, but also in the language we use, the stories we tell, the images we conjure. In today’s France it has become almost normal to say immigration and refugees are a problem, and that secularism is threatened by the very presence of Islam. France has swung to the right in recent years; the right has been radicalised and hijacked by many of Le Pen’s ideas. The Socialists are divided and in disarray. As for the radical left, it is awkwardly in tune with Le Pen on issues such as globalisation and trade – not to mention the shared, populist narrative of a clash between two supposedly homogeneous blocs, “the people” and “the elite”.

If Le Pen is soundly defeated in the presidential runoff (as polls currently predict, whoever her opponent might be), the relief democrats will feel could well be short-lived. With the Front National set to enter parliament in large numbers one month later, France will continue to look like the sick man of Europe. The fallout will be huge, and felt far beyond its borders.

These are bleak times for France – even by the standards of a country that has a taste for debating its national decline

France is a founding member of the European project, the second-biggest economy in the eurozone, the largest military power on the continent, and a permanent member of the UN security council. It is one of the pillars of the west. With Le Pen woven into its political fabric, France will hover on the edge of illiberalism, its economy hobbled by unemployment and lack of reform, its social cohesion further damaged by slogans of intolerance and division, its citizens ever more distrustful of anything that smacks of officialdom and institutions.

These are bleak times for France – even by the standards of a country that has long had a taste for “chic spleen” and debating its “national decline”. Walk into a bookshop and the covers jump out at you: Understanding France’s Unhappiness, The Twilight of French Elites and French Disintegration are just a few.

Never has an election cycle appeared so unpredictable and daunting for France’s mainstream postwar parties. The faultlines run so deep on major issues such as the welfare state, labour markets, Europe, globalisation, diversity and secularism that they have become impossible to paper over. As old structures crumble, there is a rush to the extremes.

Such is the backdrop to the “Penelope gate” scandal, which has engulfed François Fillon, the rightwing contender under investigation for suspected misuse of parliamentary funds. In desperation he has radicalised his stance, flirting more closely with Le Pen’s identity politics. But by doing so, he has helped to legitimise her populism.

France’s history of far-right movements looms large in this toxic mix. There was a whiff of 1930s politics in the air in the runup to the pro-Fillon rally in Paris last Sunday. Ultra-conservative Catholic groups had initially chosen to frame the event as a popular uprising against judges and the media. In his speech, Fillon ultimately stepped back from that anti-democratic rhetoric. But he did nothing to backtrack on vague, conspiratorial notions of a “political assassination” and a “plot” against him. The hysteria Fillon has brewed up may not save him (in fact, his polling figures have plunged further) Meanwhile, the person who stands to gain is Le Pen. A climate of demagoguery is what she craves.

The result of all of this is that most French democrats currently place their hopes on the 39-year-old former economy minister Emmanuel Macron (now polling second behind Le Pen for the first round). With his positive message of youth, optimism, reform, embracing diversity and the European project, Macron may yet prevent dark forces from prevailing. But his political base remains fragile, whereas Le Pen’s is strong.

Unknowns could yet roil the campaign, such as – God forbid – a terrorist act or a massive Russian-connected hacking and disinformation campaign, either of which would be likely to benefit Le Pen. Remember, this is a country officially “at war” since the January 2015 Charlie Hebdo and Hypercacher attacks, still under a state of emergency.

It is no exaggeration to say the fate of democracy in France and in Europe is at stake. In his 1940 book The Strange Defeat, the historian Marc Bloch analysed the collapse of France’s Third Republic. It merits rereading. “Persuasion was replaced by emotional suggestion,” wrote Bloch, describing the violent political passions of the era. To a degree, France faces a similar dilemma today. Will it, as Bloch said, “vibrate blindly to the magnetism” of populists or “know”, on the basis of sound information, that it can “consciously follow the representatives it has chosen for itself”? Democrats are watching with anxiety – and they are right to worry.