Ten candidates made it through the complicated legal obstacle course to run for president of France, but aside from the four major candidates, the only one who has had an impact on the current campaign is a woman who was a political backroom manipulator who never before had run for public office.

She is Marie-France Garaud, 47, former power behind president Georges Pompidou and then-prime minister Jacques Chirac, now the Gaullist Party presidential candidate and one of the "Gang of Four" she has been attacking.

By challenging all of them for softness toward the Soviet Union, Garaud has forced them, even Communist Party candidate Georges Marchais to a certain extent, to drop their deliberate ambiguity toward Moscow. In the words of a high French Foreign Ministry official identified with the policies of President Valery Giscard d'Estaing: "Marie-France forced the dropping of a taboo against the use of a vocabulary that was regarded here as too reminiscent of the cold war. What she has done is revealing."

She was depicted at one point in the campaign as a shepherd watching over her flock with a submachine gun across her knees. From the clouds, like the voices that Joan of Arc heard calling upon her to save France, comes the call of "Marie-France, Marie-France."

Asked recently what her favorite reading was, the first thing she listed was the political testament of Cardinal Richelieu, the 17th century French statesman who was the ultimate power behind the royal throne. She repeatedly has told interviewers that she reluctantly decided to go public only because all of the major male candidates were disappointingly softminded.

She expresses resentment that reporters, male and female, inevitably talk about her tailored Chanel sutis, practically the uniform of nonleftist French women in politics, and the way she wears her hair in an elegant chignon. When state television offered her a spot on a political talk program with the other two women candidates, both extreme leftists, Garaud said, "This is not a zoo for exotic animals." She went on the air with a male candidate. On another television appearance, she denounced the panel of pro-government reporters to their faces as "bootlickers."

The main target of her considerable repertoire of barbs has been Giscard. She made fun this week of his penchant for establishing close personal relations with foreign statesmen while seeming to ignore that states are "cold monsters." In his dealing with Soviet President Leonid Brezhnev, Garaud said, Giscard makes her think of "a dragonfly trying to charm a cold monster." s

Immediately after Garaud's systematic attack on his foreign policy, the Frency president came on the screen in a taped interview about his diplomacy and his relations with other world leaders. A close presidential adviser admitted that her rebuttal beforehand of the incombent produced a devastating effect on Giscard, who had originally intended to center the defense of his seven-year term on his foreign affairs record.

While occasionally attacking what she has called Socialist Party candidate Francois Mitterrand's "artistic haziness," Garaud clearly prefers him to Giscard despite the Socialist's need for communist votes to defeat Giscard in the runnoff election May 10 between the top two candidates.

The Garaud effect first seemed to work inside the Gaullist camp by getting former prime minister Michel Debre to shift from cursing both the Soviet and American houses to condemning Moscow's expansionism.In turn, Chirac, the most important of the three Gaullist candidates, started denouncing the Kremlin after having noticeably avoided foreign policy statements. Goscard then hardened his tone toward the Soviets somewhat.

In this increasingly anti-Soviet political climate, Marchais wound up disvowing what was generally seen here as an endorsement by the Soviet Communist Party newspaper Pravda of Giscard's reelection. Mitterrand was then able to make a frontal attack on Giscard for being soft on the Soviets, a move that greatly enhanced his standing with the large numbers of Gaullists voters who are disenchanted with Giscard.

Socialist insiders say they realistically expect to pick up 10 to 20 percent of the Gaulist vote in the runoff. They hope it will be more than enough to compensate for stay-at-home Communists.

Garaud is not expected to get more than 2 or 3 percent of the vote in the elimination round on April 26, two weeks before the runoff. But after her indictment of Giscard's foreign policy, it would be difficult for anyone who votes for Garaud to switch to Giscard.

Her efforts to tear down Giscard have culminated as the last public opinion polls that may be legally published before the elections were issued today. While different polls showed a broad spread in their results, they all showed about the same general trend with Giscard declining significantly lower than the 32 percent of the first-round vote he got in the 1974 presidential election, Mitterrand staying steady with a little less than a quarter of the vote and Chirac and Marchais both coming up in what seems like a close race for third place.

Giscard strategists had been saying privately that he would be in trouble if he did not get 30 percent in the first round voting this time. None of the most recent polls show him doing that well.

Garaud recalls that despite her inexperience as a candidate, she has been at the heart of two successful presidential campaigns -- Pompidou's in 1969 and Giscard's in 1974. As a team with highly secretive fellow-lawyer Pierre Juillet, who seems to be masterminding her campaign from his sheep farm in southwestern France, Garaud was Chirac's mentor when he acted to split the Gaulist vote in Giscard's favor and went on to his reward as the centrist president's first prime minister.

She says that she would again help Giscard's election if the circumstances were the same as in 1974, when Mitterrand was running as the Socialist-Communist unity candidate with the danger of Communist Party participation in government. Now she notes that Mitterrand is no longer formally tied to the Communists and that his conditions for a new alliance with them would mean their abandoning their allegiance to Moscow.

At the time, however, she and Juilet worked against the then-Gaulist candidate, former prime minister Jacques Chaban-Delmas, because, they said, his New Deal approach was leading France straight to socialism.

The Garaud-Juillet team persuaded Chirac to resign as Giscard's prime minister in 1976 and start challenging him within the ruling coalition.

That left France's leading gray eminences without a political front man. There was no hesitation about which of them should go public. Juillet, said Garaud, "is a man of reflection and silence. I am more outgoing. And I like to fight."