French Socialists debate their future. The troubled party, facing widespread voter disapproval, may battle over finding a more moderate, pragmatic path at party congress

Will France's Socialists disavow socialism? That tantilizing question hangs over a crucial three-day party congress which opens today in Toulouse. Following three years of economic austerity at home and a summer of embarrassment over the Greenpeace scandal abroad, the Socialists are widely expected to lose next spring's parliamentary election. At this last big party gathering before the vote, more and more Socialist faithful seem to be moving away from President Franois Mitterrand and demanding that all remaining strains of Marxist thinking be removed from its party platform.

For years, the electoral landscape here has been split between left and right. Campaigns were marked by ideological battles. A move by the Socialists, the country's main party of the left, to a more pragmatic path would turn politics here into an almost American-style competition between Democrat and Republican.

The Socialists' anti-Marxist banner-holder is Michel Rocard, who openly describes himself as a ``social democrat.'' He has long pitted his moderation against President Mitterrand's more orthodox left-wing rhetoric.

In balloting leading up to the congress, Mr. Rocard won close to a third of the votes by party members, shocking the Mitterrand majority. Before, party workers largely opposed Rocard.

Some believe that the French bombing of the Greenpeace boat Rainbow Warrior in July, which threatened to sink the Mitterrand government's reputation, and the government's austerity policy have led to Rocard's new-found popularity. Rocard resigned from his post as Minister of Agriculture last March. Since then, Rocard has been overheard congratulating himself for his sharp ``sense of smell.''

Long-term forces were also at work. When Mitterrand won power in 1981, he executed sweeping changes to ``socialize'' France, nationalizing much of the country's business and banks. Then he switched gears. During the last three years, he has tightened government budgets, presided over plant closures, and permitted unemployment to mount, all in the name of economic efficiency. While often continuing the talk of an orthodox left-winger, Mitterrand began governing like a moderate.

The contradiction has helped Rocard, whose greatest problem has always been that he lacked party backing. Even now, the majority of Socialists would not endorse him for president. Instead of pursuing Rocard's policy of trying to win over middle-of-the road voters alientated by leftist dogma, many in the party, including party leader Lionel Jospin, want to emphasize leftist credentials and win back disenchanted working-class members.

Mitterrand has tried to please both sides. He continues his tough economic policies. At the the same time, he is initiating job-training programs and encouraging investment in depressed industrial regions. He told audiences in Britanny this week he would like to see the Socialists mount a united campaign.

That means that the feuding factions will have to agree on a common platform at the congress. Rocard plans to submit one motion; Mr. Jospin another. Dramatic bargaining will likely ensue if the two are to be combined.

Failure to succeed would produce a damaging split. Socialist officials warn that the party could be so damaged that it might no longer be able to present a credible alternative to the conservatives. Rocard himself said this week that he hoped a ``synthesis'' of the two motions could be reached so that ``socialism could be renewed.'' Jospin agreed, saying that ``we must integrate into our discourse the lesson of the facts.''

The statement hints that he might agree to strip away the last Marxist remnants and publicly embrace free enterprise in the new platform. This is exactly what Rocard seeks. As he said this week, ``I feel a heavy responsibility for the renovation of French socialism, in order to turn it into a force adapted to the modern world and capable of helping lead France along the right track.''