Mr Rocard, 62, a former prime minister, pushed out Mr Fabius, another former prime minister, in a stormy meeting following the Socialists' humiliation in last month's National Assembly election.
Mr Rocard remains the most likely candidate to represent the Socialists in the next presidential election in two years' time, but his party position has seemed precarious at best.
However, in a meeting of the party's leadership over the weekend, his presidency of an initial internal set-up, to be replaced by a new permanent structure after a Socialist congress later in the year, was reinforced by support from Pierre Mauroy, the mayor of Lille and President Francois Mitterrand's first prime minister from 1981 to 1984.
Supporters of Mr Fabius, 46, who was travelling in the provinces with the President, boycotted the meeting under Mr Rocard's chairmanship.
But they later decided to accept an offer of eight seats in the new 28-member executive bureau, an institution which had been suspended on 3 April. Their decision, a serious concession, gave a legitimacy to Mr Rocard's takeover and strengthened his position in the run-up to the presidential poll.
Mr Rocard lost his own seat in the parliamentary election after he had enlivened a dull campaign by calling for a 'big bang' to re-invigorate the left and bring in allies from dissident Communists to centrists and ecologists. His anger with Mr Fabius, 46, was largely motivated by Mr Fabius' view that the Socialists should resign themselves to losing the presidential election.
Some of the younger members of the Socialist leadership made a discreet plea - described as 'a nun's fart' by President Mitterrand - to Jacques Delors, the European Commission President, to declare his own intention to be the Socialist candidate. Mr Delors, however, has declined to make the move and his hesitation seems now to have benefited Mr Rocard although, in the current pro-conservative political mood, the swing needed to make any Socialist a serious contender seems unattainable.
Mr Rocard's behaviour when he took control, when he described Mr Fabius' departure as 'the defeat of arrogance', angered many Socialists and looked as though it might break up the party. Jean-Pierre Chevenement, the left-wing former defence minister, left the party altogether.
Another crucial indication that Mr Rocard had managed to rally the bulk of the Socialist membership came when Daniel Percheron, the first secretary of the important Pas-de-Calais Socialist federation and a former Fabius ally, turned up.
Going together with Mr Mauroy's Nord federation, this meant that Mr Rocard had much of the Socialist heartland behind him.
Jean Glavany, the new Socialist Party spokesman and former chef de cabinet to President Mitterrand, said the latest Socialist meeting would enable the party to get over its internal quarrels. This is the essential prerequisite for the Socialist Party to survive into the post-Mitterrand era.Reuse content