French left-wing voters cast their ballots in a presidential primary aimed at producing a socialist candidate strong enough to confront formidable conservative and far-right rivals in the coming general election.

The preliminary rounds include seven potential presidential candidates, who left-wing voters hoped to strengthen on Sunday to confront right-wing opponents in the May 2017 general election.

Manuel Valls, the centre-left former prime minister, was among the candidates.

France's left has decreased in popularity in recent years after President Francois Hollande's economic reforms caused his socialist party to split.

As a result, the elections have brought about several candidates whose programmes are reflective of leftist ideals.

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Some candidates criticised Valls' lack of socialist principles as they associated him with Hollande.

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The former economy minister who quit Hollande's government amid feuding, Arnaud Montebourg pledged his own economic policies. One policy would be to force business owners to raise employees' wages if they raised their own.

As he cast his ballot, Montebourg said he hoped to "bring together the other components of the left-wing and win this presidential election".

Former government minister Benoit Hamon promised to tax robots, legalise cannabis and grant a "universal income" of more than $600 a month to all French adults, including the poor.

"I voted for Benoit Hamon because to me he is the one best placed to redress the Socialist party," said Jean Claude, from the small town of Millau.

However, some struggled to make a decision at the polls.

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Parisian Francoise Danzon said: "I think Montebourg's and Hamon's programmes are really on the left side, and they are interesting."

He added: "But I don't really believe in it, totally, because to me it doesn't seem really realistic."

The socialist vote is evaporating

The socialists' primary is viewed as a crucial test of the party's ability to survive and even reinvent itself in upcoming rounds.

"Turnout is much lower than the last socialist primary five years ago. By midday, some 400,000 had voted. That is very disappointing," said Al Jazeera's David Chater, reporting from Paris.

"Last year, at the republican, conservative primaries, they got four million votes. It's a real indication that the socialist vote is evaporating here," he added.

Polls, however, show majority support for conservative candidate Francois Fillon, and National Front leader Marine Le Pen.

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Overshadowing the left-wing voting is the nationalist sentiment that helped drive Donald Trump's successful campaign for the US presidency and in several countries around Europe.

Le Pen, along with other European far-right parties gathered for a conference in Germany's Koblenz on Saturday, in a show of strength ahead multiple upcoming European elections this year.

At the conference, Le Pen claimed recent anti-establishment victories by President Donald Trump and the Brexit campaign, as those of a rising populist right in Europe, adding that Europe was about to "wake up".

Al Jazeera's Chater said France's next leader would "bear the burden of Francois Hollande's legacy - the most unpopular president in French modern history".

Socialist Party leaders expect up to two million voters to cast ballots in the upcoming primary round on January 29, out of the more than 40 million citizens registered on electoral rolls.

With voters across Europe moving to the right, most polls currently show a Fillon-Le Pen win is the most likely scenario in May.

Chater added that the socialists "don't have much of a chance ... they don't have a fight in this election against Marine Le Pen".