France's Gaullists, nominally part of President Valery Giscard d'Estaing's center-right coalition, are going all-out to ensure his defeat in the forthcoming -- even at the price of a victory by Socialist challenger Francois Mitterrand.

Although the Gaullists are split at least four ways, three of the four major factions are concentrating their fire against the incumbent president, viewed by them as a traitor to the heritage of Gen. Charles de Gaulle and a threat to survival of the Gaullist movement.

The only significant Gaullist support for Giscard comes from the fourth faction, made up primarily of 10 full ministers and junior ministers serving in the Cabinet. Led by Justict Minister Alain Peyrefitte and Defense Minister Robert Galley, the ministerial faction was officially read out of the Gaullist party, formally known as the Rally for the Republic, last week. t

Then the leading Gaullist candidate, Jacques Chirac, the party chief and mayor of Paris, went on to say publicly for the first time that Giscard's defeat may be the "the price" for giving France back its "confidence and hope." Turning on its head the winning Giscardist slogan in the last presidential election -- "Change Without Risk" -- Chirac labeled the prospect of Giscard's reelection "Risk Without Change."

That was a reference to the widely heard view among Gaullists that if Giscard is reelected to a second seven-year term, it is highly unlikely that he could serve out 14 years in office without there being some sort of major upheaval like the near-revolution of May-June 1968 that nearly deposed De Gaulle after 10 years in power.

Although Giscard and Chirac are on their best behavior when they talk about each other publicly, the personal animosity that led Chirac to resign as Giscard's prime minister in 1976 is well documented and obviously still lively.

Chirac's supporters have no trouble going along with their leader's feelings because most of them agree that one of Giscard's main priorities would be the destruction of the Gaullist party in an effort to turn Giscardism into a permanent center-right majority with no need for concessions to any allies.

This widely held perception of Giscard's designs on the Gaullist electorate led a number of top Gaullists as long as two years ago to start seeking "convergence" with the Socialists. In the process, the Gaullists recalled that De Gaulle's heritage has its socialistic side, known as "Social Gaullism," and that Gaullists and Socialists worked together harmoniously in a number of postwar cabinets.

A top Chirac man said he did not think his leader could avoid giving a formal endorsement to Giscard in the runoff election May 10 between the two top vote-getters. "But," the strategist said, "there are quite a number of ways of endorsing someone, ranging from enthusiasm to damning him with faint praise."

The fragmentation of the Gaullists seems to be a now largely outdated reaction to what was once a widely held view that Chirac had let Giscard make major inroads into Gaullist support. The unexpected punchiness of Chirac's campaign has changed all that.

As the "barons" of Gaullism contemplated what they evidently saw as the bleak future toward which Chirac was leading them, they sought strategies for pesonal and factional survival. Some of them were clearly responding to Giscardist encouragement to undercut Chirac by reinforcing former prime minister Michel Debre's strong inclination to run as the embodiment of Gaullist doctrinal purity.

Justice Minister Peyrefitte, leader of the governmental Gaullists, is obviously out to establish a personal image as France's leading advocate of law and order. Giscard's liberal supporters find Peyrefitte's authoritarian rhetoric embarrassing. But, as one said, "Without Peyrefitte, the Cabinet would fall."

Chirac and the two other Gaullist candidates have been avoiding personal attacks on Giscard, leaving to the press references to alleged scandals of the Giscard presidency like his acceptance of diamonds from deposed emperor Jean-Bedel Bokassa. But the Gaullists have been so basically critical of Giscard's economic and foreign policy records and so relatively easy on Mitterrand that a large number of Gaullist voters seem bound to vote for the Socialist leader in the runoff that will almost certainly match Giscard against Mitterrand.

The other Gaullist candidates are Debre, 69, and Marie-France Garaud, 47, once one of Chirac's main political mentors. She has emerged from her traditional backroom role to run for public office for the first time because, she said, none of the other candidates is willing to stand up and be counted against the threat of Soviet expansionism.

Her insistent concentration on that theme appears to have forced the other Gaullists and Giscard to be distinctly less gentle on the Soviets than they would have been. Her effect on the foreign policy themes of the campaign seems to be out of all proportion to the 3 or 4 percent of the vote she is likely to get. Paradoxically, the indications are clear that the candidate she most trusts on the Soviet issue is Mitterrand, who needs most of the Communist vote, as well as a significant percentage of the Gaullists, to win. c

Affectionately known as "Michou la Colere," or "Angry Mickey," Debre has a number of pet themes like the patriotic need for Frenchwomen to make more babies so that France's population can be doubled to 100 million. Such Debre ideas generally produce knowing smiles. While no one was smiling at his opening campaign blasts against the way Giscard's stewardship has reduced France's standing in the world, those themes have since been effectively taken over by Chirac.

The three Gaullists have stressed their respect for each other, so much so that French political analysts generally reckon they are not really mutually damaging. It is expected that the total vote of the three will be a few percentage points higher than if there had been just one Gaullist candidate since each of them has a slightly broader appeal in a different direction than the rock-hard traditional Gaullist constituency, reckoned to be about 20 percent of the electorate.

If the 48-year-old Chirac can poll better than 13 or 14 percent in a total showing of 20 percent or more for the Gaullists, most analysts figure he will have preserved his political figure intact. At the rate he is going, he seems likely to do significantly better than that, perhaps even eating into the 30 percent that Giscard strategists say their man needs in the first-round voting so that the president can enter the runoff in a comfortable situation.

Beyond what the polls show, the reaction of Giscard and Debre campaign strategists to Chirac's dignified feistiness demonstrates that they think he is hurting them. A number of Gaullists who started out supporting Debre are known to be reconsidering now that Chirac is doing so well, especially among such traditional Giscardist voters as small businessmen. The Gaullist chief has preempted from Giscard a strong appeal to fiscal conservatism. Mayor Jacques Medecin of Nice, a good weather vane and an old Giscardist, has just jumped on the Chirac bandwagon.

Apparently stung by accusations that he is aping a Reaganite right-wing conservatism that is inappropriate for France, Chirac recently said that his program really has no relation to President Reagan's. The Gaullist said that his labor, state economic planning and worker participation ideas would "probably make Reagan's hair stand on end." That change in Chirac's pitch put him closer to potential harmony with Socialist Mitterrand.