Jean-Luc Mélenchon, the most quarrelsome man in French politics, has achieved something unprecedented in the history of La Gauche Française.

President Emmanuel Macron’s Centre is squabbling. The Right is deeply divided. The most united tribe in French politics as the June parliamentary election approach is the perennially scattered Left.

The Gauche  has often come together to fight elections in the past but always around a consensual, moderate “party of government”. Mélenchon has built an electoral alliance around his own anti-market, anti-Nato, anti-EU, anti-American, anti-German, some say anti-democratic, radical party, La France Insoumise.

READ ALSO Why France’s parliamentary elections are important

It is an extraordinary achievement. It is also an imposture – an optical illusion, an exercise in trompe d’oeil. The Greens, Communists and Socialists have signed up for the New Popular Ecological and Social Union to save their parliamentary skins.   

Without some kind of deal with Mélenchon – emboldened by his 22 percent of the vote in the first round of the presidential election – they risked near-exclusion from the new National Assembly.

Worse, they might have to forego their share of the €37 million a year in public subsidies which goes to parties which do well, or even reasonably well, in parliamentary elections.

The Socialist Party, in power until five years ago, has  become a vassal of the Socialist renegade Mélenchon, in order to survive. In doing so, it looks likely to fall apart.

Even before the National Council of the party rubber-stumps the electoral alliance, leading Socialists are jumping ship. They include the party’s last prime minister, Bernard Cazeneuve and the President of Brittany, Loïg Chesnais-Girard. Others will follow.

 Some soon-to-be-ex Socialists, including several of the party’s remaining 28 deputés, may run independent campaigns in the first round of the parliamentary elections on June 12th.

The dissidents object to any deal with Mélenchon, a rancorous man who has spent the last 20 years insulting his former Socialist party colleagues. They object in particular to the Eurosceptic, even Europhobic, tone of the common platform adopted by the Ecological and Social Union.

 Although watered down by the Green party (EELV) and then again by the Socialists, it still speaks of “disobeying” or “derogating” (temporarily withdrawing) from European Union rules on the economy (ie free competition and trade) and the size of national budget deficits. It also insists that a putative Left government would never break national or EU law.

How can both be true? They cannot. The Popular Union’s programme is just as dishonest on European Union membership as the manifesto pedalled by the Far Right leader, Marine Le Pen. It implies a kind of Frexit by disobedience: a Red Frexit which dare not speak its name.

Much of the rest of the programme – including returning to 60 as the standard retirement age and freezing fuel and food prices – is also incoherent. It runs counter to the core policies of other non-Mélenchoniste elements of the alliance.

A freeze on fuel prices? Really, Greens? Abandoning nuclear power? Weren’t we told that nuclear energy was precious to the Communists?

But there is an even greater imposture by the Popular Union: the suggestion that it can win an overall majority of the 577 seats in the National Assembly on June 12th and 19th and impose Jean-Luc Mélenchon as prime minister and de facto ruler of France.

There is little likelihood that the Left can win an overall majority of seats. With Mélenchon as self-declared “candidate for Prime Minister” there is no chance at all. The posters created by La France Insoumise with the slogan “Mélenchon Premier Ministre” are an effective campaign tool – for Emmanuel Macron.

The parliamentary elections will be fought by three almost exactly equal forces of Left, Centre and Right.

The Right is hopelessly divided between its two Far Right movements, the Lepennists and the Zemmourists and the weakened and internally split centre-right ex-party-of-government, Les Républicains.

 Each of these parties will run competing candidates in most places in Round One. Their chances of reaching Round Two in enough seats to win a parliamentary majority are zero.

The pro-Macron Centre is divided between four or five parties or factions, including Macron’s own centrist party, La République en Marche. Difficult and bad-tempered negotiations are under way to allocate the 577 seats to a single “Macronist” candidate. They will succeed – eventually.

The Left is nominally united behind Mélenchon’s  Popular Union. Blocs of seats have been allocated to its four main components and a couple of smaller fragments. They will do reasonably well. They will probably win more seats united than they would have won separately. But they will not win a majority.

Why not? In theory more than one candidate can reach round two. But the bar for a third candidate is very high if turnout is, as expected very low. To reach the second round a candidate must score 12.5 percent of the registered electorate in Round one. If turnout is below 50 percent, as seems likely, that means 25 percent of the actual vote or more. There was only one “triangular” second round contest out of 577 five years ago.

In the second round in June wherever a Mélenchon candidate faces a Macron candidate, there will be a surge of right-wing votes to defeat the Mélenchoniste Left. In other words, the parliamentary elections will resemble the presidential elections in reverse. A Harris Interactive poll this week suggested that Macron’s camp might win well over 300 seats and the grand Mélenchon alliance less than 100 – even though the Left may have more votes overall in Round One.

I expect that the outcome on June 19th will be somewhat tighter than that.

Mélenchon repulses many people (including many on the moderate Left). But he also inspires many young people and residents of the multi-racial suburbs, who usually vote little. In the first round of the presidential election, Mélenchon outscored poll predictions because he turned out the young Metropolitan and banlieue vote in larger than expected numbers.

If he can do that again on June 12th (possible but doubtful), the Left can win many more than 100 seats the following week. It might just conceivably help to deny Macron a working majority.

But in rural and better-heeled constituencies, Mélenchon is more scarecrow than pied-piper (cf Jeremy Corbyn). There are not enough Mélenchon-friendly, Metropolitan and suburban seats for the Left to force Macron to surrender de facto power to Mélenchon or any other left-wing prime minister.