After a tumultuous election campaign filled with scandal and surprises, French voters will decide on Sunday whether a pro-European Union centrist or an anti-EU, anti-immigration far-rightist will lead them for the next five years.
Opinion polls indicate they will pick Emmanuel Macron, a 39-year-old ex-economy minister who wants to bridge the left-right divide, resisting an anti-establishment tide that has seen Britons vote to leave the EU and Americans choose Donald Trump as US president.
But should an upset occur and National Front candidate Marine Le Pen win, the very future of the EU could be on the line.
Mr Macron, who wants to deregulate the economy and deepen EU integration, has a 23-26 percentage point lead over Ms Le Pen in the opinion polls.
Forecasts proved to be accurate for the presidential election's first round last month and markets have climbed in response to Mr Macron's widening lead over his rival after a bitter debate on Wednesday.
In a campaign that has seen favourites drop out of the race one after the other, Ms Le Pen, who wants to close borders, ditch the euro currency and clamp down on migration, is nevertheless closer to elected power than the far right has ever been in Western Europe since World War II.
Even if opinion polls prove accurate and France elects its youngest President ever rather than its first female leader, Mr Macron himself has said himself he expects no honeymoon period.
Abstention could be high and close to 60 percent of those who plan to vote for Mr Macron say they will do so to stop Ms Le Pen from being elected to lead the euro zone's second-largest economy rather than because they fully agree with the former banker-turned-politician.