Three French Socialists put themselves forward as potential candidates to run in next year's presidential elections.
After an internal ballot of the party's 200,000 members, Segolene Royal won the nomination.
Ms Royal, 53, was the only woman candidate and the most popular, with a 30- to 40-point lead over her closest rival going into the ballot, according to opinion polls among Socialist voters.
Recent polls have also shown she is the only candidate capable of beating right-wing Interior Minister Nicolas Sarkozy in the presidential race.
A former environment and family affairs minister, she is currently the leader of the south-western Poitou-Charentes region.
She has shocked fellow Socialists in past months with tough plans to cut crime and by questioning the party's key 35-hour working week policy.
Critics say she is a political lightweight with no experience of big ministerial posts and vague, populist policies that sometimes lean to the right.
Supporters say the mother-of-four brings a new style to jaded politics and is trying to establish a genuine rapport with the French electorate.
One of the old-guard Socialists, the 57-year-old former finance minister and economics professor portrays himself as a "radical reformist", but many in the party accuse him of wanting to usher in liberal policies through the back door.
The charismatic DSK, as he is known for short, was widely credited with engineering the revival of the French economy in the late 1990s under Socialist Prime Minister Lionel Jospin.
As a multilingual former economics professor and a trained lawyer, he is a respected figure in the business community at home and abroad.
A father of four, he is married to the respected political journalist and former TV presenter Anne Sinclair.
In 1999, he was forced to resign following allegations of forgery. A court later cleared him, and he returned to politics as a deputy.
There has been speculation in the media that he may have struck a deal with Ms Royal to be her prime minister if she wins the presidency.
The former Mitterrand prime minister, aged 60, is a political heavyweight who has occupied most of the top jobs in French politics.
More recently, he split the party in 2005 by lobbying to reject the EU constitution in the French referendum - against the party line. He argued that the text was a vehicle for Anglo-Saxon economic liberalism.
He was sacked as deputy leader of the party after France voted "No" to the constitution in the referendum.
Ahead of the ballot, Mr Fabius sought to capitalise on the charter's defeat by courting left-wing voters with promises of a "more social Europe" and an immediate rise in the minimum wage if elected.
He is alleged to have said when it emerged Ms Royal was interested in running for president: "But who's going to watch the children?"