The PS was founded in 1969 from a merger of the French Section of the Workers' International (SFIO), the Convention of Republican Institutions led by François Mitterrand, and other groups.

During his term, Hollande battled with high unemployment, multiple Jihadi terrorist attacks, poor opinion ratings and a splinter group of Socialist MPs known as frondeurs (rebels).

Facing the emergence of centrist Emmanuel Macron and left-winger Jean-Luc Mélenchon, PS candidate Benoît Hamon finished 5th in the 2017 presidential election.

Together with the Radicals, who wished to install laicism, the SFIO was a component of the Left Block (Bloc des gauches) without to sit in the government.

In 1934, the Communists changed their line, and the four left-wing parties came together in the Popular Front, which won the 1936 elections and brought Blum to power as France's first SFIO Prime Minister.

Indeed, for the first time in its history, the SFIO obtained more votes and seats than the Radical Party and it formed the central axis of a left-wing parliamentary majority.

Supported by all the left-wing parties, he obtained a good result and faced De Gaulle in an unexpected second ballot, becoming the leader of the non-Communist left.

The two parties failed to update the Common Programme and the PCF leader Georges Marchais denounced a "turn towards the Right" of the PS.

For the first time since 1936, the Socialists scored better in the polls than the Communists, becoming the main left-wing party, but their defeat caused an internal crisis.

[22] In 1981, Mitterrand defeated the incumbent conservative, Valéry Giscard d'Estaing, to become the first socialist of the Fifth Republic to be elected President of France by universal suffrage.

Mitterrand attempted to carry out socialist-inspired reforms (the 110 Propositions), furthering the dirigiste economic planning trends of the preceding conservative governments.

Workers' wages were increased and working hours reduced to 39, and many other sweeping reforms carried out, but the economic crisis continued.

Although there were two periods of mild economic reflation (first from 1984 to 1986 and again from 1988 to 1990), monetary and fiscal restraint was the essential policy orientation of the Mitterrand presidency from 1983 onwards.

[23] The PS lost its majority in the French National Assembly in 1986, forcing Mitterrand to "cohabit" with the conservative government of Jacques Chirac.

Furthermore, a part of the left wing of the party, led by Jean-Pierre Chevènement split off due to his opposition to the Gulf War and the Maastricht Treaty.

Rocard lost the most part of his followers after his 1994 electoral crash, Fabius was weakened by the infected blood scandal, the presidentiability of Emannuelli was questioned.

Finally, Lionel Jospin, who had announced his political retirement after the loss of his parliamentary seat in 1993, came back and proposed to "take stock" of Mitterrand's inheritance.

Benefiting from a good image in the polls, a strong loyalty to the party (as former First Secretary) and governmental experience (as former Education Minister, and the teachers were numerous and influential in the PS), he defeated Emmanuelli in the internal ballot.

Then, he was defeated by Jacques Chirac in the run-off election but, given the PS crisis, his result was judged good and he returned as First Secretary.

He announced his retirement from politics, and the PS called on its supporters to vote for Chirac in order to defeat the far-right National Front leader Jean-Marie Le Pen, who had surprisingly advanced to the run-off.

François Hollande, who became First Secretary in 1997, was re-elected in 2003 during the Dijon Congress with the support of the main Socialist personalities, against the left wing of the party.

Virtually all factions agreed on a common agenda, broadly based on the moderate and pro-European majority's position with some left-wing amendments.

[24] Many potential candidates appeared for the 2007 presidential election: François Hollande, Laurent Fabius (from the left wing of the party), Dominique Strauss-Kahn (who claimed to represent "social democracy"), Jack Lang, Martine Aubry and Ségolène Royal, who was favoured according to the polls.

Immediately after her defeat several party bosses (notably Strauss-Kahn), held Ségolène Royal personally responsible for the unsuccessful campaign.

At the same time, some personalities of the right wing of the party (such as Bernard Kouchner) accepted to join the government nominated by Nicolas Sarkozy.

Some candidates proposed to succeed François Hollande, who had announced he will not compete for another term as First Secretary: In the pre-vote, the text of Royal arrived the first with 29%, followed by Delanoë (25%), Aubry (25%) and Hamon (19%).

Though he had not officially declared his candidacy, Dominique Strauss-Kahn, a prominent member of the Socialist Party and the managing director of the International Monetary Fund was the polls' clear favorite to defeat the incumbent conservative president, Nicolas Sarkozy.

The idea for holding an open primary to choose the Socialist Party presidential candidate had first been suggested in 2008, by the independent left-leaning think tank Terra Nova.

It was also set against the fragmentation of the left between three major candidates, with polls indicating that the party's candidate would come in fifth, behind the National Front's Marine Le Pen, François Fillon of the centre-right Republicans, Emmanuel Macron, former economy minister under Hollande who founded his centrist political movement, En Marche!, and left-wing ex-Socialist Jean-Luc Mélenchon under the banner of La France insoumise.

On 12 October 2018, MEP Emmanuel Maurel left the party together with other elected officials and founded the Alternative for a republican, ecologist and socialist program (APRÉS).