For their final TV debate, the seven candidates held nothing back to ensure they secure the Socialist primary nomination.
As in the first of the three debates, left-wing rebel Benoît Hamon, who resigned from the government in 2014, stood out with his proposal of a universal basic income.
"My plan may be the most radical one her," he told viewers. "I'm giving you a choice, one in favour of social progress. A universal income will change our attitude to work."
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Yet it comes at a hefty price tag of 300 billion euros, roughly the equivalent of France's total budget, a point the other contenders didn't fail to attack him on.
Only Jean-Luc Bennahmias, of the small Democratic Movement, backed him up.
"Benoît, don't give up," he told his rival. "It's the only new idea we've had for years.3
But the former education minister is rising in the polls.
Anti-austerity made in France
The anti-austerity ex-finance minister has wooed the public with his promise to promote products "made in France", starting by granting 80 percent of all public contracts to small businesses.
"I belong to that group of Socialists who don't give up," he said. "Who know how to take on the rich and powerful. This is the story of my life. What would France look like without the left?"
Montebourg and his rivals could soon find out.
Polls show centre-left coming fifth
According to the latest polls, whoever wins the Socialist nomination is unlikely to even make it to the second round of the presidential elections in April.
In opinion polls former prime minister Manuel Valls is behind independent Emmanuel Macron, conservative candidate François Fillon and far-right leader Marine Le Pen
Valls is betting on an appeal to left-wing voters' loyalty.
"Be proud of who you are: Socialists and Republicans, French men and women, who uphold our secularist values," he appealed to them. "Go and vote, massively, and choose tomorrow, once again hope, which I embody."
Yet this message is likely to ring hollow for many Socialists, who accuse Valls of selling out the left, in pursuit of a pro-business agenda.
At the end of this third debate, dominated by questions over Europe, protectionism and how to counter the perceived threat posed by Donald Trump, it is unclear, whether the candidates have done enough to convince the undecided.