Pairs: Emmanuel Macron launched his bid for the French presidency on Wednesday, a move likely to take votes from mainstream candidates in a tight race that promises a strong turnout for far-right leader Marine Le Pen and humiliation for the left.
The former investment banker, who until August was Socialist President Francois Hollande's economy minister, will stand as an independent in next year's presidential election.
Although among France's most popular politicians, the 38-year-old does not hold elected office and has no party apparatus behind him, so his campaign may struggle. He also has yet to set out his policies in any detail.
However, he is widely seen as likely to take votes from conservative Alain Juppe, the current favourite to win the presidency, and who is fighting a tightening race for the centre-right nomination in a presidential primary election starting on Sunday.
At his launch in an apprenticeship centre northeast of Paris, Macron said he wanted to move France away from "clan-based politics", adding: "I've witnessed the shallowness of our political system from the inside."
He said the best way for France to deal with globalisation was closer ties with the rest of Europe, in contrast to the inward-looking policies of some other contenders.
Juppe has fought his campaign so far on a similarly pro-European and centrist platform, positioning himself to the left of his main rival, Nicolas Sarkozy.
Ex-president Sarkozy in turn has sought to appeal to populist voters with sharp criticism of European Union policy and of Hollande's track record on security and immigration that resonate in France after a series of militant attacks in France and with Europe in the grip of an immigration crisis.
Polls until this week showed 71-year-old former prime minister Juppe winning the primaries of the Les Republicains party and its centre-right allies, beating off Sarkozy's challenge.
Juppe was then expected to be propelled in the election itself by voters of the mainstream right, centre and left, all determined to keep the popular anti-EU, anti-immigration National Front leader Le Pen from power.
They still mostly show that scenario, but on top of the Macron move, fresh poll readings in recent days ahead of a last television debate on Thursday point to a "third man", Francois Fillon, potentially spoiling the Sarkozy-Juppe scenario.
In the background too is a feeling that more surprises might be on their way.
Donald Trump's unexpected victory over Hillary Clinton for the US presidency raised the prospect that surveys might still be failing to capture the full scale of the populist vote being courted by Sarkozy and Le Pen, despite assurances from French pollsters that they take full account of the potential for "hidden" far-right votes.
Le Pen was in a confident mood on Wednesday.
"Macron is the banks' candidate," she said at the launch of her campaign headquarters.
"What is for sure is that he will not be stealing any of our voters. This is a candidate that smells of mothballs."
Juppe, who may have more to worry about, went on the attack, saying Macron had stabbed Hollande in the back by quitting.
Juppe's other problem is Fillon, who was Sarkozy's prime minister between 2007 and 2012, and who is gaining ground fast in the Les Republicains contest while Juppe's support has slipped.
An Opinionway poll out on Tuesday shows Fillon neck-and-neck with Sarkozy in second place for the first round of the primaries, and then, should he edge Sarkozy into third place, beating Juppe in the second round to take the nomination.
Fillon has espoused Thatcherite free market policies in determinedly dirigiste France, and wants to cut up to 600,000 public sector jobs - even more than Sarkozy, but is also seen as a "lightweight" version of his former boss on security and immigration.
Other polls in recent days have also shown Fillon gaining votes as Juppe loses them. Much of Juppe's support is seen as an ephemeral "least-worst" choice, while the abrasive Sarkozy's backers are more hard-core in his favour.
Macron quit the French government at the end of August to set up his own political movement called "En Marche", which translates as "Forward" or "Onwards".
Macron's campaign organisers said they had amassed 2.7 million euros ($2.89 million) of funding from 6,400 donors to date. The official spending cap in the 2012 campaign was about 21 million euros.
An October poll by Odoxa made Macron the most popular of potential presidents from the left, with 49 per cent considering him a good head of state. Prime Minister Manuel Valls came second on 42 per cent. Hollande trailed on 13.
So Macron's presence in the contest as the only independent - a rare phenomenon in French presidential elections - is also likely to further fragment the divided left-wing vote as speculation grows that Valls will stand instead of the deeply unpopular Hollande against an array of others.
Hollande's trade minister Matthias Fekl said Macron's candidacy would "explode the left".
"This was a time bomb placed at the heart of a political family. The bomb has exploded," he said on RMC radio.