In a landslide of historic proportions, the French Socialist Party appeared today to have won more than enough votes in the first round of the two-stage pday to have won more than enought votes in the first round of the parliamenary elections to emerge next Sunday with an absolute majority of the French National Assembly.

It would be only the second time in this century that a single party wins a parliamentary majority. The previous time was when the Gaullists won the majority in 1968 in reaction against the May-June worker-student revolt.

With vote counting ended for the night, almost complete returns gave the Socialists and their close allies, the Radicals of the Left, 38 percent of the vote -- the same as the Gaullists in 1968 -- and the combined forces of the left better than 55 percent.

The Socialist result demonstrated a dramatic bandwagon effect after the May 10 election of Socialist leader Francois Mitterrand, who received 52 percent of the vote of defeat incumbent President Valery Giscard d'Estaing. pMitterrand got 25.8 percent of the vote in the first round of the presidential election April 26, about 12 percent less than today's Socialist showing.

Gaullist leader Jacques Chirac, who won his own personal seat outright today with more than half the votes cast, conceded that the Socialists are likely to win an absolute majority in the assembly. In 1968, the Gaullists wound up with nearly 300 of the assembly's 491 seats.

Gaullist Party Secretary General Bernard Pons, reflecting a widely heard conservative complaint that the French people have been hypnotized into a state of false "euphoria," said, "The voters have been living in a dream world since May 10. Everything is seen through rose-colored glasses. Everything is beautiful."

The Communists today got only about 16 percent of the vote. That represented a failure to bounce back from its 45-year low point April 26, when Communist leader Georges Marchais got 15.3 percent of the presidential vote. cSocialist candidates outpolled Communist incumbents, including a number of Communist leaders, in many districts, and the Communist parliamentary representation was expected to be halved from 86 in the old assembly.

Socialist spokesman wee cautious in their comments about the Communist results. Socialist first secretary Lionel Jospin said they were "perhaps historic." Prime Minister Pierre Mauroy said they "might represent the rejection of a party line." Jospin pledged that the Socialist would not abuse their power as he alleged the center-right majority had done against the leftist opposition. He said they would get fair treatment in the state-controlled electronic media and in parliament.

The Socialist held 117 seats in the 491-member lower house elected in 1978 and dissolved by Mitterrand as the first act of his presidency. The Gaullists had 155 and the Giscardists l33.

The Socialists elected 49 deputies outright with more than half the votes cast today, and were comfortably leading in 199 runoffs, according to the Ministry of the Interior. Candidates getting 50 percent of the vote were declared winners. In 1978, not a single Socialist was elected on the first round. The Communists won seven seats today and were well-placed to win in 35 others. The Gaullists took 50 and led in 24 others, and the Giscardists won 50 seats and led in 11. Fifty races appeared too close to call, and not enought results were in to judge in 14 districts.

The Socialists got almost as much as the combined vote of the Gaullists and Giscardists, who had huddled together to back each other's incumbent deputies in the first round. The combined vote of all the center-right parties was 43 percent.

There was an unusually large number of nonvoters -- nearly 30 percent, the largest abstention rate in 20 years. Despite appeals tonight by center-right leaders for the nonvoters to rally to them in the runoff elections next Sunday, most independent analysts say the nonvoters are split along the same lines as the voters. This was demonstrated in last month's presidential election, when about 5 percent more of the 36.4 million registered voters came out for the runoffs but gave the combined Left about the same percentage.

The key question of Communist participation in the Cabinet remained open, with the Socialists still refusing to commit themselves until after the runoffs. Communist leader Marchais confirmed tonight his party's agreement with the Socialists to withdraw in favor of each other's front-running candidates, an accord that is expected to help the Socialists in the overwhelming number of cases.

Top Communists who trailed Socialists included at least six of the 21 Politburo members -- deputy party leader Charles Fiterman; Paris leader Paul Laurent; foreign affairs spokesman Maurice Gremetz; Pierre Juquin; Roland Leroy, publisher of the party newspaper L'Humanite; and Gisele Moreau. She was outdistanced by National Solidarity Minister Nicole Questiaux, who got 36.4 percent of the vote in the 13th Arrondissement or district, of Paris, compared to the incumbent Moreua's 24.4 percent.

Among Socialists elected outright today were Prime Minister Mauroy; Defense Minister Charles Hernu; Science and Technology Minister Jean-Pierre Chevenement, head of the party's official left wing; and Budget Minister Laurent Fabius, the party's chief spokesman when it was in opposition. Also elected was former Radical Party leader Maurice Faure, now justice minister.

The spectacular showing of the Socialists made it likely that Mauroy would be renamed as prime minister. Mitterrand intimates had said that someone with broader appeal to the center-left would be named prime minister if the Socialists had needed to make an appeal to their right to form an assembly majority.

Among the Gaullists elected today were former prime ministers Pierre Messmer, Jacques Chaban-Delmas, former foreign minister Maurice Couve de Murville, former interior minister Christian Bonnet, former justice minister Olivier Guichard and airplane manufacturer Marcel Dassault, 89, the oldest member of the assembly.

Some of the Giscardists elected outright included former prime minister Raymond Barre, former interior minister Raymond Marcellin and former deputy foreign minister Olivier Stirn.

Prominent Socialists well-positioned to win next week included Mitterrand's former rival Michel Rocard, now economic planning minister; African Cooperation Minister Jean-Pierre Cot; Agriculture Minister Edith Cresson; First Secretary Jospin; Mitterrand intimate Roland Dumas, a leading civil right lawyer; Gisele Halimi, a top leader of the women's liberation movement, and Mitterrand's son Gilbert.

Former Gaullist prime minister Michel Debre was also expected to win his runoff in the Indian Ocean island of Reunion. But the two most prominent Gaullists in the Giscrd government, former justice minister Alain Peyrefitte and Defense Minister Robert Galley, were in tight races that they could lose.