However, a late surge for Jean-Luc Mélenchon, the ex-socialist running an insurgent campaign against the established political class, has expanded the field into a three-way race. (Republican candidate François Fillon has seen his support remain solid around 18 per cent in the face of corruption scandals, but with zero growth in weeks he’s fading fast).

A desire for change seems to be a common denominator, as voters on the left and right have abandoned the traditional Socialist and Republican parties for a trio of new parties promising to shake up the political establishment.

The French Bernie?

Wounded by high-profile defections to Macron, and bedeviled by the candidacy of a grumpy sexegenarian leftist who attracted over 11 per cent of the vote in 2012, Socialist leader Benoît Hamon has floundered. In the past weeks, his support has dropped into single digits in some polls, as the French left appears to consolidate around the candidacy of a crotchety old man promising massive reinvestments in social programs.

The comparisons to a certain U.S. senator are inescapable.

Is this career politician, long an outsider even within the Socialist Party for his leftist views, experiencing the kind of popular rebirth that Bernie Sanders rode to a series of victories in the Democratic primaries?

Like Sanders, Mélenchon’s campaign focuses on class inequality and speaks to a groundswell of anger against the super-rich and the political establishment. Also like Sanders, Mélenchon combines strident calls for social justice with a sharp critique of the fossil fuel industry, calling for a rapid transition to renewable energies. And like Sanders, Mélenchon and his ideas are experiencing a sudden and unexpected resurgence.

The similarities between these insurgent campaigns are no accident. Mélenchon’s communications director, in fact, spent considerable time in the U.S. observing and learning from Sanders’ campaign, especially its use of social media and digital mobilization strategies.

Mélenchon has a strong presence across all social media platforms, and has innovated by using holographic projections to address multiple campaign rallies simultaneously. Last week his campaign even released a video game, Fiscal Combat, in which the candidate literally shakes down the rich to gather money for his social programs.

It appears to be working.

Polls over the past week, dozens of them, confirmed by several more released today, all show the same thing: a sudden surge in support for Mélenchon, as he draws even with or passes scandal-plagued former prime minister François Fillon for third place.

That still leaves him roughly five points back of the front runners, Macron and Le Pen, with what may be too little time to close the gap and propel himself into the second round of voting.

But in politics, momentum is everything, and as Mélenchon has surged his opponents have all stagnated or lost support, setting up an interesting finish over these last days of the campaign.

Mélenchon’s moment

Win or lose, it’s a storybook finish to a long political career for Mélenchon, who announced at the beginning of the campaign that this would be his last election.

On Sunday, an estimated 70,000 people packed into a public square in Marseilles to hear him excoriate France’s political elites, and promise peace, a 32-hour work week and a 100 per cent tax on the super rich. It’s one of many rallies in recent weeks to draw crowds in the tens of thousands.

Meanwhile, the share of French voters who think Mélenchon would make a good president has doubled in some polls, an unprecedented increase in the history of presidential election polling.

Other polls shows as many as 40 per cent of voters remain undecided, and the volatility of the electorate paired with the late surge for Mélenchon have analysts contemplating the possibility of a second-round showdown between candidates of the far left and right.

On Tuesday, the head of a business lobby group, Medef Pierre Gattaz, went on a popular radio station to warn against a second round matchup between Mélenchon and Le Pen, describing their platforms as “an absolute catastrophe” for France.

It’s a showdown that polls suggest Mélenchon would win handily. In that, he is not alone. Second-round polling has Le Pen losing by a wide margin to all of her closest competitors in head-to-head matchups. She may make it to the second round, but appears to have little chance of capturing the presidency.

Oddsmakers take notice

Had you placed a bet early last month on Mélenchon to win, you would have gotten pretty good odds. Not so today. Responding to the latest round of polls, British bookmaker Betfair dropped the odds on his candidacy again today, to a new low of 11:1. Last month they were at 979:1.

That implies his odds of becoming president have improved from 0.1 per cent to around 12 per cent.

“If Mélenchon continues to gain ground and Macron continues losing it with Le Pen holding hers,” Naomi Totten, a spokesperson for Betfair, told Business Insider, “this presidential race could potentially become a far-right versus far-left battle in the second round.”

Macron, by contrast, remains the favourite with odds of 5:6, or a slightly better than 50 per cent chance of winning.

The likeliest outcome remains a second-round showdown between Macron and Le Pen; however, continued gains for Mélenchon could see him displace one or the other, and there is no disputing that his late surge has made him the dark horse of this race.

For those of us watching from afar, the time has come to start paying attention. The next two weeks could get interesting.