If the far left and far right were as distinctively different as we are given to believe, then Nicolas Sarkozy would now be short odds to retain the French Presidency when he goes head to head in the second round of the election against the Socialist candidate François Hollande.

If you add the first-round votes gained by the Front National candidate Marine Le Pen to those for Sarkozy, the total would put him six points ahead of the aggregate of Hollande's first round votes combined with those of Jean-Luc Mélenchon, the hard-left candidate backed by the Communists. Yet the fact remains that Hollande is the clear favourite with the bookmakers to win in the second round and become President of the Republic.

Assuming that they are right (and bookmakers tend to be), this is a beautifully clear demonstration of the truth that, at the fringes, the terms left and right can be highly misleading. In this case, the anti-capitalist rhetoric of Hollande will appeal to many of those who previously voted for Marine Le Pen: distrust, even hatred of international commerce, is something that ultra-nationalist parties share with the far left – and not only in France. Anyone who has troubled to read the manifestos of the British National Party will have found many policies almost indistinguishable from those put forward by, for example, Arthur Scargill's Socialist Labour Party.

The BNP calls for the renationalisation of privatised industries and rejects what it calls "the globalisation scam". It says that "the owners of industry should work and the workers should own. Strong trade unions are vital to protect the workers from exploitation." Most recently, the BNP candidate for the London Mayoral elections, Carlos Cortiglia, has spoken of the need for "socialist principles" in the public services.

Students of history will see no paradox in this. As FL Carsten observed in The Rise of Fascism, "Mussolini had a profound contempt for those whose overriding ambition was to be rich. It was, he thought, a kind of disease. He declared he was fighting the socialists, not because of their socialism "but because they were anti-national". Mussolini's British imitator, Oswald Mosley, left the Labour Party because it had rejected his plans for vast public expenditure on "investment", combined with outright protectionism: his New Party, soon to become the British Union of Fascists, set out exactly such a programme.

In the first round of the French election both Mélenchon and Le Pen openly advocated protectionism – which, after all, is the only logical antithesis to the despised "globalisation". Le Pen talked about "social and economic protectionism", the "social" aspect obviously directed against immigrants, while Mélenchon referred to what he termed "European protectionism": this sees the EU as an extension of France's battle against the perceived tidal wave of cheap goods from China and other expanding nations in the developing world (now perceived as an even bigger threat than the old arch-enemy, America).

As Sophie Meunier observes in the current issue of Foreign Affairs magazine, the anti-globalisation rhetoric is almost mandatory in French politics, and "dominates the current electoral season". She points out that Hollande and Sarkozy "both understand that globalisation" – international trade, in plain English – "is essential to France's economic growth [but] neither can really say so aloud ... they will both continue to defend free trade staunchly but by stealth, hiding their actions behind rhetoric to appease the pessimistic public."

If it is true that Hollande and Sarkozy truly are free traders (which would make them rare creatures within the French political class) then it makes their pandering to the culture of pessimism even more reprehensible: seven million French jobs depend on exports and in 2010 France was, among all the world's nations, the fourth largest recipient of foreign direct investment.

The markets, it seems, have taken the view that François Hollande means what he says in his trenchant attacks on "finance". French shares fairly plummeted yesterday. Yet since almost 60 per cent of France's public sector debt is held by foreign investors and next year the country will need to borrow a sum equivalent to 20 per cent of GDP just to roll over its current loans, it is hard to imagine that a President Hollande would actually wish to engage in such a war on "international finance", even supposing it were possible within the confines of the so-called euro stability pact. Marine Le Pen has at least been consistent in calling for France to exit the euro, which would involve a colossal default on its debts: in that sense Hollande, unlike the far right, is merely a paper tiger in the battle with international capital.

Besides which, Hollande is hardly too young to recall what happened after François Mitterrand was elected to the presidency in 1981, with the backing of the Communists, on a platform of tackling the flagging economy with a massive public sector stimulus. He faithfully carried it out. The minimum wage was raised sharply; 250,000 government jobs were created; 38 banks were nationalised; transfer payments were boosted under the Allocations Familiales programme. It was a disaster. Unemployment and inflation took off and the franc was devalued three times in a desperate effort to keep the country's exports competitive as domestic costs soared and productivity waned.

Two years later Mitterrand declared that he'd been "intoxicated" by his vision of Keynesian economic stimulus and switched abruptly to a new policy: "La Rigueur" – or austerity. The result was that by the middle of the decade, the national budget was in balance, and inflation had dropped back to a manageable 4 per cent. It seems unlikely that Hollande would want to repeat the Mitterrand economic roller-coaster ride – and, as I say, it would in any case not be possible if France wishes to retain its membership of the euro as now constituted.

Yet it would serve one valuable purpose if the next French government were to adopt the protectionist anti-globalisation policies so apparently popular with disenchanted voters. It would be a proper economic experiment; policymakers (and the wider public) could draw the appropriate empirical conclusions from the outcome.

Does full-blooded socialism work? There's only one way to find out – though I wouldn't care to bet on a different outcome to every other time it's been tried.