The French began voting on Sunday in an election that will decide whether pro-European Union, centrist President Emmanuel Macron keeps his job or is unseated by far-right eurosceptic Marine Le Pen in what would amount to a political earthquake.

Opinion polls in recent days gave Macron a solid and slightly growing lead as analysts said Le Pen — despite her efforts to soften her image and tone down some of her National Rally party's policies — remained unpalatable for many.

But a surprise Le Pen victory could not be ruled out, given the high numbers of voters who were undecided or not sure if they would vote at all in the presidential runoff.

With polls showing neither candidate able to count on enough committed supporters, much will depend on a cohort of voters who are weighing up anxiety about the implications of a far-right presidency against anger at Macron's record since his 2017 election.

If Le Pen does win, it would likely carry the same sense of stunning political upheaval as the British vote to leave the European Union or the US election of Donald Trump in 2016.

Polls opened at 8 am (0600 GMT) and will close at 8 pm (1800 GMT). Initial projections by pollsters are expected as soon as polls close.

In Douai, a mid-sized town in northern France where Le Pen was ahead of Macron in the first round of voting two weeks ago, pensioner Andre Loeuillet, 69, said she had voted for Macron, as she did on April 10.

“He has his faults but he has qualities too. He is the one best placed to continue, we are living through difficult times,” she said.

Macron, 44 and the winner in the same matchup five years ago, has warned of “civil war” if Le Pen — whose policies include a ban on wearing Muslim headscarves in public — is elected and has called on democrats of all stripes to back him.

Le Pen, 53, focused her campaign on the rising cost of living in the world's seventh-largest economy, which many French say has worsened with the surge in global energy prices. She has also zeroed in on Macron's abrasive leadership style, which she says shows an elitist contempt for ordinary people.

“The question on Sunday is simple: Macron or France,” she told a rally in the northern town of Arras on Thursday.

Dislike for Macron

Among early voters in the village of Souille, near the northwestern town of Le Mans, civil servant Pascal Pauloin, 56, said he had voted for Le Pen out of disenchantment with Macron.

“Frankly, I am very disappointed. Our France has not been working well for years. Macron has done nothing for the middle classes, and the gap with the rich is getting ever wider,” he said.

Le Pen, who has also been criticised by Macron for her past admiration of Russian President Vladimir Putin, rejects accusations of racism.

She said her plans to give priority to French citizens for social housing and jobs and scrap a number of welfare benefits for foreigners would benefit all French, independently of their religion or origins.

Jean-Daniel Levy, of Harris Interactive pollsters, said opinion surveys showed Le Pen was unlikely to win, because that would require huge shifts in voter intentions.

If Macron prevails he will face a difficult second term, with none of the grace periods that he enjoyed after his first victory, and protests likely over his plan to continue pro-business reforms, including raising the retirement age from 62 to 65.

If she unseats him, Le Pen would seek to make radical changes to France's domestic and international policies, and street protests could start immediately. Shockwaves would be felt across Europe and beyond.

Whoever comes out on top, a first major challenge will be to win parliamentary elections in June to secure a workable majority to implement their programmes.