Marine Le Pen and her National Front party are the focus of elections for more than 2,000 councils across France.
Opinion polls rate Ms Le Pen’s party as the favourite against the ruling Socialists and conservatives ahead of today’s vote.
The result could prove crucial in building Ms Le Pen’s grass-roots base if, as expected, she runs for president in 2017.
The National Front’s opposition to immigration, radical Islam, the European Union and the euro has helped transform the party from a pariah under Ms Le Pen’s father.
France’s council elections are in two rounds, so victory today will determine which candidates can contest a second vote on March 29.
Candidates appear on ballots in pairs – one male, one female – to ensure that 50% of council members are women.