After a tumultuous election campaign filled with scandal and surprises, the French public began to vote on Sunday on 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.

Macron, who wants to deregulate the economy and deepen EU integration, has a 23- to 26-percentage-point lead over Le Pen in the opinion polls.

Forecasts proved to be accurate for the presidential election's first round last month, and markets have risen in response to 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, 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 Two.

Even if opinion polls prove accurate and France elects its youngest president ever rather than its first female leader, Macron himself has said himself he expects no honeymoon period.

Marine Le Pen and Emmanuel Macron traded insults during the debate

Abstention could be high, and close to 60 percent of those who plan to vote for Macron say they will do so to stop 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.

"The expected victory ... wouldn't be a blank cheque for Emmanuel Macron," Odoxa pollsters said in a note. "A huge majority will not be backing him wholeheartedly."

Sunday's election will in any case not end of the battle between mainstream and more radical policies in France, with parliamentary elections next month equally crucial.

Once the presidential ballot is over, attention will immediately switch to whether the winner will be able to count on a parliamentary majority. The first poll on the parliamentary election, published this week, showed that was within reach for Macron.

Much will also depend on both the candidates' score on Sunday. Le Pen's niece, Marion Marechal-Le Pen, on Thursday told L'Opinion daily that a 40 percent score would already be "a huge victory" for the National Front.

Whoever wins will spell a new chapter in French politics. The major left-wing and right-wing parties -- the Socialist Party and The Republicans -- that have ruled France for decades both suffered humiliating defeats in the election's first round.

French Presidential Election Show all 20 1 /20 French Presidential Election French Presidential Election Voters line up to cast their ballots REUTERS French Presidential Election French expats queue along the street outside the Lycee Francais Charles de Gaulle to cast their vote in a polling station inside the school, in the first round of the 2017 French presidential election, in London, Britain April 23, 2017. REUTERS/Luke MacGregor - RTS13JM5 REUTERS French Presidential Election People line up to vote in the first round of 2017 French presidential election at a polling station in Vaulx-en-Velin near Lyon, France, April 23, 2017. REUTERS/Emmanuel Foudrot - RTS13HSP REUTERS French Presidential Election Police patrol polling stations in France REUTERS French Presidential Election Francois Fillon (L), member of the Republicans political party and 2017 French presidential election candidate of the French centre-right, casts his vote in the first round of 2017 French presidential election in Paris, France, April 23, 2017. REUTERS/Christophe Archambault/Pool - RTS13IH0 REUTERS French Presidential Election Benoit Hamon (C), French Socialist party 2017 presidential candidate, is surrounded by photographers as he leaves a polling station after voting in the first round of 2017 French presidential election in Trappes, near Paris, France, April 23, 2017. REUTERS/Vincent Kessler - RTS13I0Y REUTERS French Presidential Election French President Francois Hollande collects voting slips before casting his ballot in the first round of the 2017 French presidential election at a polling station in Tulle, France, on April 23, 2017. REUTERS/Georges Gobet/Pool - RTS13ITO REUTERS French Presidential Election A policeman walks by election posters near a polling station during the first round of 2017 French presidential election in Paris, France, April 23, 2017. REUTERS/Christian Hartmann - RTS13I3A REUTERS French Presidential Election Emmanuel Macron and wife Brigitte Trogneux REUTERS French Presidential Election Emmanuel Macron casts his ballot REUTERS French Presidential Election Emmanuel Macron, head of the political movement En Marche !, or Onwards !, and candidate for the 2017 French presidential election, waves hand during in the first round of 2017 French presidential election at a polling station in Le Touquet, northern France, April 23, 2017. REUTERS/Benoit Tessier - RTS13ICH SAA/ French Presidential Election Jean-Luc Melenchon, candidate of the French far-left Parti de Gauche and candidate for the French 2017 presidential election, leaves a polling booth in the first round of 2017 French presidential election at a polling station in Paris, France, April 23, 2017. REUTERS/Stephane Mahe - RTS13IKB REUTERS French Presidential Election Front National leader Marine Le Pen casts her ballot Marine Le Pen (L), French National Front (FN) political party leader and candidate for French 2017 presidential election, casts her ballot in the first round of 2017 French presidential election at a polling station in Henin-Beaumont, northern France, April 23, 2017. At R, Mayor of Henin-Beaumont Steeve Briois. REUTERS/Charles Platiau - RTS13IEI REUTERS French Presidential Election Early ballots are read as results continue to come in Reuters French Presidential Election Macron supporters react as results come in early in the evening AP French Presidential Election Supporters of Front National leader Marine Le Pen cheer as early results come in Reuters French Presidential Election Alamy Live News. J21KYW Paris, France. 23rd April 2017. Marcon supporters wave French and EU flags after the announcement that he is the leader in the exit polls after the polling stations have been closed. Supporters of Emmanuel Macron, the Presidential candidate from the social liberal political party En Marche! celebrate the exit polls, that see him in first place, ahead of Marine Le Pen from the Front National in the first round of the French Presidential election. Credit: Michael Debets/Alamy Live News This is an Alamy Live News image and may not be part of your current Alamy deal . If you are unsure, please contact our sales team to check. Alamy French Presidential Election Front National leader Marine Le Pen takes to the stage to address her supporters as fans cheer Reuters French Presidential Election Emmanuel Macron greets supporters on Sunday night AP French Presidential Election Emmanuel Macron and wife Brigitte Trogneux celebrate the incoming results EPA

The campaign was hit by yet another surprise on Friday night just before the quiet period which forbids politicians from commenting started. Macron's team said a massive hack had dumped emails, documents and campaign-financing information online.

Some 67,000 polling stations opened at 8 a.m. Pollsters will publish initial estimates at 8 pm (1800 GMT), once all polling stations are closed.

More than 50,000 police officers will be on duty. Security will be a prime concern in the wake of a series of militant attacks in Paris, Nice and elsewhere in the past few years that have killed more than 230 people in the past two-and-a-half years.