President Emmanuel Macron stunned France when he called the vote after his centrist alliance was crushed in European elections this month by Marine Le Pen's National Rally (RN). Her eurosceptic, anti-immigrant party was a longtime pariah but is now closer to power than it has ever been.
Polls close at 2am on Monday AEST in small towns and cities and at 4am AEST in the bigger cities, when the first exit polls and seat projections for the decisive second round a week later are expected.
However the electoral system can make it hard to estimate the precise distribution of seats in the 577-seat National Assembly, and the final outcome will not be known until the end of voting on July 7.
Marine Le Pen's National Rally trounced Emmanuel Macron's centrist party in European elections. (AP PHOTO)
"We are going to win an absolute majority," said Le Pen in a newspaper interview, predicting that her protege, 28-year-old Jordan Bardella would be prime minister.Â
Her party has a high-spending economic program and seeks to reduce immigration.
If the RN does win an absolute majority, French diplomacy could be headed for an unprecedented period of turbulence: with Macron - who has said he will continue his presidency until the end of his term in 2027 - and Bardella jostling for the right to speak for France.
France has had three periods of "cohabitation" - when the president and government are from opposite political camps - in its post-war history, but none with such radically divergent world views competing at the top of the state.
Bardella has already indicated he would challenge Macron on global issues. France could lurch from being a pillar of the EU to a thorn in its side, demanding a rebate of the French contribution to the EU budget, clashing with Brussels over European Commission jobs and reversing Macron's calls for greater EU unity and assertiveness on defence.
A clear RN victory would also bring uncertainty as to where France stands on the Russia-Ukraine war. Le Pen has a history of pro-Russian sentiment and while the party now says it would help Ukraine defend itself against Russian invaders, it has also set out red lines, such as refusing to provide long-range missiles.
Opinion polls have suggested the RN has a comfortable lead of 33-36 per cent of the popular vote, with a hastily assembled left-wing coalition, the New Popular Front, in second place on 28-31 per cent and Macron's centrist alliance in third on 20-23 per cent.
National Rally leader Jordan Bardella could become prime minister after the elections. (EPA PHOTO)
The New Popular Front includes a wide range of parties, from the moderate centre-left to the hard-left, eurosceptic, anti-NATO party France Unbowed, led by one of Macron's most vitriolic opponents, Jean-Luc Melenchon.
How the poll numbers will translate into seats in the National Assembly is hard to predict because of how the election works, said Vincent Martigny, professor of political science at the University of Nice and the Ecole Polytechnique.
Candidates can be elected in the first round if they win an absolute majority of votes in their constituency, but that is rare. Most constituencies will need a second round involving all candidates who received votes from at least 12.5 per cent of registered voters in the first round. The top scorer wins.
For decades, as the far right steadily gained popularity, voters and parties who did not support it would unite against it whenever it edged closer to national power, but that may not hold true this time.
Le Pen and Bardella have sought to make their party's image more acceptable to the mainstream, for example by denouncing antisemitism. Le Pen's father Jean-Marie Le Pen, founder and long-term leader of the RN's forerunner, had a history of overtly antisemitic comments.
But critics say the RN's courting of Jews is just a cover allowing it to deny accusations of racism while constantly stigmatising Muslims and foreigners.
