Many observers had written off the French left before this year's presidential elections, but then Jean-Luc Melenchon, the head of La France Insoumise (LFI, which roughly translates as France Unbowed), started gaining popularity. 

Though Melenchon, an eloquent defender of the people, narrowly missed it into the runoff, he immediately made clear that, if he could not be president, he could at least be prime minister. He said that should voters gave his party a majority in the National Assembly, he would rectify the policies of French President Emmanuel Macron.

Against all odds, the former Socialist was able to forge an alliance with rival left-wing parties, which agreed to run on a joint ticket under the acronym NUPES, for Nouvelle Union Populaire Ecologique et Sociale (New Ecological and Social Popular Union). 

The first round of the parliamentary elections , on June 12, ended up being a very tight race between NUPES and Macron's Ensemble (Together) alliance, with the latter beating the former by a fraction.

This did not prevent Melenchon from announcing that night that NUPES was the real winner and claiming that the presidential party had been "beaten and defeated."

Though this was a gross exaggeration, there is no doubt that NUPES has turned the tables. "This electoral alliance has completely shifted the political dynamic in France, from the presidential election to the parliamentary election," says Thomas Manz, the head of the Paris office of the Friedrich Ebert Foundation, which is affiliated with the German Social Democrats.

It was a political feat that Melenchon was able to convince the Socialist, Communist and Green parties to join NUPES, whose dominant force is LFI, and agree to present one candidate only per constituency.

'Out of necessity'

For a long time, such an alliance had been deemed unlikely. This was partly because of political differences, but also because many distrust Melenchon, particularly members of the Socialist Party, which he left in 2008, believing that it had become too "liberal" and "social democratic." He immediately founded the Parti de Gauche (Left Party) and then relinquished the presidency in 2014 to launch LFI.

"Many Socialist mayors agreed to the alliance more out of necessity than anything else," Manz said.

Only a handful of the 577 seats in the National Assembly were allocated in the first round. The runoff election on Sunday will seal the fate of the remaining candidates. Ensemble candidates advanced to the second round in 417 constituencies; NUPES candidates did so in 380. They are the only two parties mathematically able to achieve an absolute majority of 289 seats.

A Sixth Republic?

Most pollsters forecast that NUPES will end up with fewer than 200 deputies. One important reason is that the alliance has already largely exhausted its potential amid left-wing voters and, to win an outright majority, it would have to mobilize huge numbers of nonvoters. There was historically poor turnout in the first round, so this is very unlikely.

Even if NUPES were to win an absolute majority, Macron would not be obliged to appoint Melenchon prime minister. He is free to choose his head of government, though he does have to take into account the parliamentary majority. .

The NUPES program is largely dominated by LFI policies. Melenchon wants to dismantle the Fifth Republic and set up a Sixth Republic, with what he says would be a fairer political system. He has promised voters better social benefits if he wins, though he has struggled to explain how these would be funded. Macron plans to increase the retirement age to 65; NUPES has promised to lower it from 62 to 60. The alliance also would cap prices for basic foodstuffs and raise the minimum wage to €1,500 ($1,575) per month.

A particularly controversial aspect is that Melenchon has said he would disobey certain EU rules if they conflicted with France's interests. Policy toward the European Union has been the subject of much fierce debate within NUPES. Former Socialist President Francois Hollande said such a development would betray EU and social democratic history.

Challenges for Melenchon

The 70-year-old Melenchon remains popular, particularly among younger voters, and his coalition is likely to become the clear opposition in parliament. The conservative Republicains (LR) are expected to come third, and Marine Le Pen's National Rally fourth.

But, without a majority, the French constitution will give NUPES and Melenchon little opportunity to shape government policy, and it is improbable that a political deal will be made. If Macrons Ensemble alliance does not win an absolute majority, the president will probably more likely try to negotiate with LR lawmakers.

In the past five years, Melenchon has mainly tried to delay measures by introducing a flood of amendments. "This time, too, one can imagine that there will be little constructive cooperation, " Manz said. However, by tradition the strongest opposition force gets the chair of the finance committee and this would at least offer NUPES a stage, from which to make political attacks on the government.

Manz said Melenchon, who did not run for reelection in the National Assembly this year, could step away from politics should NUPES fail to beat Ensemble.  "Melenchon is a realist," Manz said. "He knows that this will have been his last chance to become president or prime minister."

Though the parties of NUPES are running on a joint ticket, they are expected to part ways after the election, apparently not wanting to form a joint parliamentary group but simply to coordinate their work in the Assembly.

Le Pen, who received 42% in the presidential runoff, is not expected to play a huge role in the new parliament. However, her party could end up at least doubling its seats, to 15 or more.

This article was originally written in German.