French Prime Minister Manuel Valls has declared his bid to become the Socialist candidate for next year's presidential election and says he is quitting the government to focus on campaigning.
The path was cleared for Valls to enter the race last week when the deeply unpopular President Francois Hollande announced he would be the first leader since France's Fifth Republic was created not to seek a second mandate.
Although opinion polls bill Valls as favourite to win a hard-fought contest for the Socialist's ticket, they also show that a run-off vote in next spring's election is likely to be fought between conservative candidate Francois Fillon and far-right National Front leader Marine Le Pen, with Fillon seen triumphing.
Valls, 54, talks tough on law and order and his business-friendly economic stance may offer his rivals from the traditional left of the party a soft target in campaigning ahead off the centre-left primaries in late January.
"Yes, I am candidate for the presidency of the Republic," Valls said to applause from supporters in his fiefdom of Evry, the gritty southern suburb of Paris where he was mayor for over a decade.
France's left is deeply divided as it approaches the election and Valls will have to disentangle himself from Hollande's five years at the helm of the euro zone's number two economy if he is to persuade voters he is the best candidate to heal the party's rifts.
"I am outraged at the idea that the left could be disqualified from these presidentials," Valls said, referring to his party's poor poll ratings and infighting.
"We must unite," said Valls, adding: "My candidacy is one of conciliation, of reconciliation."
Valls announced his resignation as prime minister, saying he would step down on Tuesday.
Health Minister Marisol Touraine and Interior Minister Bernard Cazeneuve are seen as possible choices to replace him and lead what will effectively be a caretaker government.
Valls said fighting unemployment would be his priority and pledged to lower taxes for the poorest and for the middle-class, if elected. He also vowed to protect France's social security system.
He faces a tough fight for the centre-left nomination. Several other Socialists have said they will take part in the primary, including former economy minister Arnaud Montebourg, a left-wing firebrand popular among the traditional left.
The failure of pollsters to forecast the outcome of the Les Republicains primary and the high number of undecided voters on the left mean the race is wide open.
In contrast to the left's divisions, the right has rallied behind Fillon, a 62-year-old former prime minister, who promises to slash public spending, cut half a million public sector jobs and overhaul social security.