As the French Presidentielle hots up for the final vote on Sunday week, both Macron and Le Pen are fighting bitterly for the support of the erstwhile supporters of the left-winger Mélenchon who came a very respectable third in last Sunday’s poll. From the great and the good, who detest Le Pen, there is a concerted call to all and sundry to form an anti-far-right alliance and vote for Macron (where necessary holding their noses) so as to replicate what happened in 2017.

It is fair to say that much of what is said against Le Pen is misleading. Her economic policies are if anything more Mélenchon than Macron: lowering the pension age, reducing the burden on young families, and reducing the tax on fuel. Nor is there that much difference between her present approach to Russia and Macron’s: while vocally expressing support for Zelensky, both are opposed to arming Ukraine with serious offensive weapons, and favour a broadly neutral France doing its best to avoid the fall-out. Many voters seem to be correspondingly sceptical of suggestions for a concerted anti-far-right front. I am at present briefly in France; and in my copy of Le Figaro on Wednesday morning there appeared a survey of over 300,000 respondents that showed a substantial majority against the idea.

But in one area Le Pen stands on her own: the EU. Macron is a big supporter, not only of French participation in the EU, but of more Europe, including the beginnings of a European military force. Le Pen, to put it mildly, is not. Macron, indeed, accuses her of wanting a de factoFrexit, and thus of supporting nationalism and all the conflict that supposedly goes with that. Not surprisingly, the EU establishment and supporters such as the prime minister of Luxembourg are solidly behind him; so is the rump of the Gaullist establishment and – to his slight embarrassment – the right’s enfant terrible Nicolas Sarkozy.

On Le Pen Macron has a point, though only partly. Le Pen is an EU sceptic; but her position is in essence nationalist and populist. (Indeed she relentlessly attacks Macron as an anti-democratic technocrat, and for her part supports an enormous extension of national referendums on a way of deciding matters of importance.) She sees defence as fundamentally a national matter. Consistent with her Nato scepticism, she resolutely wants to exclude EU input. And she takes the same view of other matters she sees as essential to France’s identity. She has accordingly made it quite clear that if elected she will have no compunction in passing legislation she sees as necessary to protect French workers’ interests or give effect to the will of the French people.

What Le Pen is not, however, is a Frexiteer. Although she flirted with a Leave position in the 2017 election, when she made approving remarks about Brexit, she has since publicly changed her mind. Although very much of the ‘Europe of Nations’ camp, she has now emphasised that while she is prepared to stand up to what she regards as EU bullying she stands firmly in favour of France remaining in, and at the centre of, the EU.

Ironically, one suspects that it is precisely this point that seriously spooks the EU and its supporters. The EU could deal with out-and-out support for Leave. True, France is one of the more Eurosceptic countries in the European club; nevertheless, there remains a reasonable majority in favour of membership. It follows that a French president calling for Leave could be fairly easily marginalised on the issue, with their programme unlikely to ever come to fruition.

However, a candidate formally committed to remain but at the same time publicly committing to putting France’s interests above those of the EU legal order is another matter. There is, after all, no mechanism for expelling a country from the EU. And a France that insisted on staying but refused to commit to a firm following of EU law would be a Eurocrat’s nightmare.

For one thing, France and Germany have hitherto been indispensable anchors of EU orthodoxy. Brussels already has severe difficulties in tackling Eastern European states such as Poland and Hungary which take an insouciant attitude to the supremacy of EU law and at times to the orders of EU courts. But at least hitherto Macronniste France has fairly consistently joined Berlin in taking its side. With a Le Pen administration in Paris, the Commission’s moral and political hold on Poland and Hungary would be immeasurably reduced.

But it is worse than that, at least for Brussels. A bloody-minded Le Penniste France would not only sap the EU’s authority, but would itself be another potential Poland, only this time ten times worse. Imagine that France passed populist legislation to protect French workers or the French way of life; that the EU demanded its disapplication, and that a radical French government declined either to obey (possibly backing up that decision with a referendum) or refused to pay any fine imposed by the court. The Commission would be in trouble. As France is a net contributor to the EU budget, a threat to turn off the financial taps would not have the same effect as on other member states, to whom the Commission can at least say that they should not be allowed to draw on EU largesse without obeying EU laws. And in any case the sheer political awkwardness resulting from the EU taking such drastic steps against one of its leading (and founding) members would be enormous.

For the moment, one suspects, the Commission is covering its eyes at the thought of such a catastrophe and hoping it will not happen. It might well obtain its wish. To have a chance, Le Pen needs substantial numbers of Mélenchon voters to switch allegiance to her. Those in the know seem fairly sure that this will not happen, and that most of those voters will sulk like so many socialist versions of Achilles in his tent, or at the very least not bother to vote again on Sunday week.

Le Pen, in short, is a serious threat to the EU way of doing things. But in the end but it may be that apathy, rather than any kind of right-wing front, will defeat her.