PARIS (AP) -- Hard-left Socialist rebel Benoit Hamon heads into France's left-wing presidential primary runoff as a surprising favorite to beat pro-business pragmatist Manuel Valls, in a vote that will realign France's unpredictable presidential campaign.
Hamon is the favorite in Sunday's vote after arriving in pole position in the first round with 36 percent of the votes.
He proposes a "determined and optimistic leftist alternative." His most talked-about proposal is a 750 euros ($800) "universal income" that would be gradually granted to all adults.
He is now backed by another left-wing candidate, Arnaud Montebourg, eliminated from the race with 17.5 percent of the votes.
Valls, who arrived second with 31.4 percent, criticized Hamon's "unrealistic" promises.
A former junior minister and briefly education minister, Hamon left the government in 2014. He then led a group of rebel Socialist lawmakers who opposed the government's economic policies.
"Yesterday's failed solutions have no reason to become successes tomorrow," he said at a rally near Paris Thursday.
Nassera Mohammad, living in Trappes, the suburban city west of Paris where Hamon was elected, said he believes the hard-left candidate proposes "real innovation" in French politics. "That's where we have to go, toward a renewal ... and not to be pleased with the old programs or with very small reforms," Mohammad said.
Ten French economists, including Thomas Piketty —author of the best-seller "Capital in the Twenty-First Century"— this week published an article to argue that the universal income can be "relevant and innovative".
"Properly conceived and detailed, the universal living income can be a key element for reshaping our social model," they wrote.
Valls has tried to make an asset from his experience as prime minister from 2014 to 2016 —despite his association with unpopular President Francois Hollande.
Valls promotes "authority and security" values as the country is still under threat from potential terror attacks.
He says he represents a "credible left" seeking a balance between France's social model and reforms adapting the country to globalization.
"I don't want to be the candidate of the taxes; I leave it to my adversary," Valls said in a rally near Paris Thursday. "I want to be the candidate of work value, of jobs, with a clear and serious roadmap offering a future to the French people."
Vivien Chauffaille, a Parisian attending Valls' rally, said "he is the only one able to be a statesman and implement his proposals."
The French Socialist party has been torn for years between advocates of a radical left, including Hamon and Montebourg, and others sharing center-left views, like Valls and Hollande.
Divisions are so deep that if Hamon wins Sunday, some supporters of Valls are expected to back centrist figure Emmanuel Macron, who is campaigning for president as an independent.
Early polls showed the Socialist nominee, whichever is chosen, is currently ranking at the fifth position in the race for president. Not only far-right leader marine Le Pen and conservative leader Francois Fillon appear to be far ahead, followed by Macron and far-left figure Jean-Luc Melenchon.
Another sign of the Socialist party's uphill struggle for survival is that the first round was marred by irregularities in the vote count.
Results were not in dispute, but the number of voters was. Observers suspected organizers of trying to increase it artificially in order to give their future nominee more legitimacy.
In the end, the party announced 1.6 million voters last week. More than 4 million people cast ballots at the conservative primary in November.
The primary is open to all voters who pay 1 euro ($1.04) and sign a document saying they share the left's values.