The man likely to emerge from the French presidential elections as the country's most formidable political leader, whether or hot he makes it into the runoff between the top two vote-getters, is Gaullist Party leader Jacques Chirac.

At 48, he is the only one of the top leaders representing France's four main political currents whose image is still unquestionably young and dynamic. When he entered the race, many of his political allies advised him against involvement in a political struggle in which he could only be hurt by the splits in the Gaulist movement and crushed by the electoral power of incumbent President Valery Giscard d'Estaing.

Some of Chirachs closest political friends were saying he would be lucky to get 12 percent of the vote, which would spell disaster for the Gaullist Party. Afterthree months of intensive campaigning, he has come so far that some of his top campaign workers this week mounted a last-minute public relations drive to credit the idea that in the first-round elimination vote Sunday, Chirac could displace Socialist leader Francois Mitterrand as Giscard's challenger in the runoff vote on May 10.

A Chirac adviser complained to a visitor that Chirac's campaign staff had become so overzealous that members have tried to persuade Chirac, as well as the press, that he could get more than the 18 to 20 percent of the vote that the political insiders are predicting.

The supporter laughingly waved an opinion poll that went so far as to place Mitterrand out front while showing Giscard as having fallen behind the Socialist and as running even with Chirac. Like all other polls between now and the elections, it may may legally be published.

Asked why the political parties spend their money on such polls, the Chirac supporter said: "Don't worry. The money won't go to waste. The main shareholder in that polling group is Chirac's campaign manager."

Nevertheless, some of the candidates apparently find it convenient to act as if such outcomes were possible. Speaking in Brittany yesterday, Giscard said of the prospect that he might have Chirac, his nominal coalition partner, as a final opponent.

"Be careful about a second-round vote in which there would be no opposition candidate," he said. "That would mean that half the French people could not express a political preference. I want a fair fight. I don't want to be elected by the abstention of half the French people."

Disenchantment with the president seems so widespread, observers have suggested, that if the electorte were confronted with a Chirac-Giscard choice not also involving what the French call "a choice of society," the incumbent would probably have great difficulty being reelected. Giscard's statement appears to indicate which of his two leading rivals he most fears.

Yet, Chirac's growingly insistent claim that he will be in the runoff instead of Mitterrand is likely to boost considerably Mitterrand's showing in the first round.

Many Communist voters are hesitating between helping their party make a good showing the first time around to give it political leverage over the Socialist leader and voting for Mitterrand from the start to help ensure the defeat of Giscard. Any suggestion that the Socialist might not make it into the runoff reinforces the temptation to desert Communist Party candidate Georges Marchais.

"This intoxication campaign of Chirac's is a blow against our party," said a Communist Party militat. "It just goes to show what we've been saying all along -- that Mitterrand is a candidate of the

While disclaiming that he could desire any such thing, Chirac's strategists privately concede that his political interests would be best served by a Mitterrand victory. If that happened, the Giscardist Party, a coalition of three disparate political movements -- a splinter group from the old anticlerical Radical Party, the heirs to France's Christian Democrats and Giscard's own organization, embodying the traditions of the defunct conservative and peasant party -- could be expected to fly apart.

In that case, Chirac would almost automatically stand out as the leader of the opposition to a Socialist president and the main rallying point for a broad conservative coalition.

Three important Chirac campaign staffers, interviewed separately, agreed that Chirac must personally endorse Giscard in any runoff against Mitterrand but that he is also likely to stress that no candidate owns his first-round electoral following and that everyone is free to vote as he pleases.

"Mitterrand doesn't scare anyone anymore," said Chirac campaign manager Charles Pasgua. "No one believes he would bring the Communists to power. He has reassured the moderates."

Even if Giscard is reelected after the current campaign, in which his record of seven years in office has been the major target of political dissatisfaction, he would be a lame duck whose main rival inside the moderate camp would be Chirac, who would be a pole of attraction for Giscardists concerned about their political futures.

Probably the most telling argument against Giscard's reelection by an often fickle electorate is Mitterrand's "seven years is already enough, 14 years is just too much." At 64, Mitterrand is not suspected of having more than one term in mind for himself. But the 55-year-old Giscard apparently felt constrained to pledge that, if reelected, he would not seek a third term.

Chirac has had to overcome a four-way split in the Gaullist movement. Former prime minister Michel Debre, who considers himself the guarantor of Gaullist doctrinal purity, was the first Gaullist to announce his candidacy and has refused to withdraw to give Chirac a chance to get into the runoff. Personally respected by most Gaullists for his integrity and fervor, Debre is a poor campaigner. His standing has been steadily whittled away by Chirac.

"Debre has actually rendered Chirac a great service," Pasqua said in an interview at Chirac headquarters. "He is going to do so poorly -- maybe not even 2 percent -- that we will be rid once and for all of the hold of the old Gaullist 'barons' over the movement. They will be discredited, and Chirac will be the uncontested leader."

Many of Chirac's foes concede that point to Pasqua, if only because some of the 'barons," representing the pro-Giscard faction, have in effect read themselves out of the movement by backing the president against overwhelming Gaullist hostility.

Pasqua apparently also tried to pressure the third Gaullist candidate, former Chirac adviser Marie-France Garaud, out of the race this week, in an orchestrated series of maneuvers that climaxed with a rise in the Paris stock market yesterday on a string of rumors that she was withdrawing. She called a press conference to say she was in to stay and to compare Pasqua's attempts to inflate Chirac with the efforts of the bullfrog who tries to make himself as big as a bull by blowing himself up with air -- until he bursts.

Nevertheless, the episode illustrated that, while this is Chirac's first race for the presidency, he is hardly a novice. He is generally credited with electing Giscard in the first place in 1974 by splitting the Gaullist camp against its official candidate, Jacques Chaban-Delmas. In the 1978 legislative elections, Chirac made possible the winning strategy that defeated the Socialist-Communist alliance.

In this campaign, he has shown an ability to make voters forget his past contributions to the Giscardist presidency. On Pasqua's desk was an anonymously printed campaign sticker reading, "Jacques Chirac. Yesterday, he betrayed Chaban. Today, he is betraying Giscard. Tomorrow, he will betray you." It is a message that has been drowned by a well-organized Chirac campaign across France in which the Gaullist leader has shed his old image of frenzy and authoritarianism.

Instead, he has replaced it with one of a calm, thoughtful young leader with a Ronald Reagan-like refusal to accept the economically depressing effects of international recession.

"No one wants to hear that there's nothing to be done about it," said Pasqua. "The French people are ready to hear a message like Reagan's."

Helping Chirac get his message across is his impressive record as mayor of Paris. Even his most ardent national opponents admit that he has shown he knows how to get things done at city hall.