Former French Socialist party chief Francoise Hollande has won the nomination to be the Socialist candidate in next April's presidential election.
Mr Hollande defeated current Socialist leader Martine Aubry in a run-off vote on Sunday.
In his acceptance speech, he said he was ready to challenge incumbent President Nicolas Sarkozy and usher in a new chapter in French politics.
Opinion polls suggest he could beat Mr Sarkozy, who has not formally declared his own bid.
Mr Hollande had a lead of 56% to 44% over his rival in the count.
The BBC reports it was the first time voters have taken part in a US-style primary race. Some 2.7 million voters took part.
The election takes place in two rounds on 22 April and 6 May.