France has begun voting for its next president — here's what you need to know about the election

The final stages of campaigning were overshadowed by the attack on the Champs Elysees on Thursday, but the nation is determined not to let terror get in the way of democracy.

It is likely to be the closest and most fascinating French election for some time, with eyes on far-right candidate Marine Le Pen, who could ride the wave of populism that swept Donald Trump to victory in America last year.

Sunday is the first round of the election, when a field of 11 candidates will be whittled down to two. A second vote will then take place on May 7 to determine the winner.

The first exit polls are expected to be published in France around 8 p.m. CET (7 p.m. BST/2 p.m. EDT) on Sunday, but could be delayed due to polling stations being kept open later than usual. A final result is usually published around midnight local time.

How does the French election work?

The French election system under the Fifth Republic is quite different from many others as it encompasses two voting rounds. Here's how it works:

Who are the main candidates?

Although though there are 11 candidates, only five are thought to have a realistic chance of becoming France's next president. These are the main contenders:

Emmanuel Macron,

At 39 years old, Macron could become France's youngest-ever president.

He served under President François Hollande as Minister of Economy, Industry, and Digital Data, but only truly entered the public consciousness when he rebelled against the socialist party he served and ran as an independent presidential candidate for his En Marche movement.

Macron is passionately pro-businesses and pro-EU. He built a reputation with his "Macron Law," a controversial reform bill allowing, among other things, longer retail hours on Sunday.

The most controversial candidate in the race, Le Pen is famed for her hardline anti-immigration views and opposition to the European Union.

She has taken far-right National Front party — which was founded by her father — from a marginalised voice to one of the most important forces in French politics.

François Fillon, Les Républicains

Fillon is the candidate for the centre-right Republicans party. He overcame challenges from Nicolas Sarkozy and Alain Juppé — France's former president and prime minister respectively — to clinch the nomination.

Fillon's campaign, however, has been dogged by controversy over allegations that his wife and two children improperly received public funds.

Jean-Luc Mélenchon, La France Insoumise

At first dismissed as a fringe contender, the communist candidate is now considered a dark horse. Mélenchon has impressed during the election campaign, performing particularly well in the television debates.

Benoît Hamon, Socialist Party

The former education minister defeated ex-Prime Minister Manuel Valls in the race to secure the socialist nomination, but has faced an uphill struggle selling his vision to the electorate.

The Socialist Party has grown unpopular under Hollande, who has low approval ratings, and left-wing support has drifted towards Jean-Luc Mélenchon.

What do the polls say?

Le Pen consistently topped polls for the first round of voting up until March this year, when she was overtaken by Macron. But the forecasts remain tight.

A poll, carried out before Thursday's Paris attack for BFM TV and L’Express, showed that Macron remains favourite to triumph with 24% of the vote, while Le Pen was in second place with 21.5%.

Since the attack, however, Le Pen has gained support. An Odoxa poll on Friday forecast that Le Pen will secure 23% of the vote, coming a close second to Macron, who polled at 24.5%.

Fillon and Mélenchon have generally polled in the high teens this month, while Hamon is significantly off the pace.

It would not be too much of a surprise if Macron and Le Pen are the two that progress to the second round, where it is expected that support could consolidate around the former.

What happened last time around?

In the last elections in 2012, socialist François Hollande won the second round of the election with 51.6% of the votes against outgoing conservative president Nicolas Sarkozy (48.3%).

In the first round, which had 10 candidates, Hollande garnered 28.6% of the votes, Sarkozy 27.1%, and Le Pen 17.9%. This shows the progress Le Pen has made in the past five years.

Barbara Tasch contributed reporting to this story.