A string of scandals and blunders that would have cost lesser men their political careers has failed to shake the strong grip on the levers of power that Prince Michel Poniatowski has established over the past three years.

As befits a man of his enormous girth and political appetite, the 54-year-old Poniatowski wades into controveries that others tiptoe around. His lifeline is the seemingly unshakable trust that President Valery Giscard d'Estaing has in him.

Ponia, as France's minister of interior and head of police is colloquially known, is the man who ordered the arrest of suspected Palestinian terrorist Abu Daoud last month, according to reliable diplomatic and French sources. The arrest plunged France into an international uproar.

Two weeks before, he had tried clumsily to slam the lid on a messy scandal surrounding the mysterious murder of a fellow politico-aristocrat by calling a press conference to brand as guilty two men who had not even been formally charged with the crime.

Unlike most French scandals, the murder of Prince Jean de Broglie last Christmas Eve has not faded quietly from public concern. New details continue to rise to the surface and ripple through a nervous segment of the French elite.

More typical is the quiet way in which "the Dassault affair" appears to be coming to an end. On March 6, the accountant who skipped town last July with $2 million of aviation magnate Marcel Dassault's money is to come up for a hearing to determine whether he goes free or is put on trial.

The accountant, Herve De Vathaire, threatened to sing some detailed songs about Dassault's taxes and financing of politicians when taken into custody by Poniatowski's policemen in September. There appear to have been no startling disclosures, however, and the betting in political circles now is that De Vathaire may walk away from the hearing free, even though the $2 million has not been recovered.

Cynical political handicappers think the odds for a quiet ending to the whole thing soared last week when Dassault's closest collaborator, Pierre Guillain de Benouville, announced that he was running for the City Council on the ticket of the Republican-Independent Party of Giscard and Poniatowski.

The defection was considered here to be a crippling blow to the hopes of Gaullist leader Jacques Chirac to become mayor, and Poniatowski lost no time in boasting that Chirac was now beaten.

Dassault has been a principal financier of the Gaullists, who are locked in a bitter struggle with their nominal allies, the Republican-Independents, in the Paris race.

"This is a scandal," Chirac shot back. "Mr. Poniatowski is beginning to go beyond the limits of decency.As minister of interior he organizes and supervises the election. How can he prejudge the outcome?"

The sole source of Poniatowski's power here is precisely Giscard's faith in Poniatowski's ability to handle these twin roles - chief political tactician for the small, conservative-leaning party that the two of them founded in 1966, and head of the ministry that controls the police and elections.

He is also useful as a 6-foot-2, 200-pound lightning rod for Giscard. France's tightly centralized system of government inevitably brings the country's most unsavory problems to Paniatowski's doorstep, focusing bitter criticism on him rather than on the president.

His handling of the most recent problems, however, has caused some observers to wonder whether Giscard can afford to retain Poniatowski as France girds for a battle between leftist and conservative coalitions for control of the National Assembly next year.

For the first time since Giscard's election in 1974, it is no longer out of the question that he could shift Poniatowski to another job, these observers say. A major Cabinet reshuffle is predicted after the March 20 municipal balloting.

Giscard contributed to the atmosphere of impending change today by appointing publisher and former Cabinet minister Jean-Jacques Servan-Schreiber to head a mission to conduct long-term planning toward modernizing and decentralizing French administration.

A descendant of a noble Polish family, Poniatowski is a distant cousin of Giscard's wife and reportedly is one of the few men in France who call the patrician president by the familiar French form, "tu."

Still harboring intense dislike for both Gaullists and Communists formed in his days in the French Resistance in World War II, Poniatowski hurls verbal thunderbolts at prominent politicians without regard for their party label.

His clashes with his center-right and center-left allies have been mostly over Poniatowski's demands for increased police powers and the need for faster death penalties. He formed a special anti-gang police squad that was supposed to shoot it out with gangsters - but it wound up killing more innocent bystanders than criminals before Poniatowski shelved the idea.

Probably only Poniatowski could have ridden out the storm that his decision to arrest suspected terror leader Abu Daoud in Paris on Jan. 7 brought down on Giscard's administration.

The official accounts of the arrest of the Palestinian leader, accused by Israel of having organized the 1972 attack on the Olympic village in Munich, have been deliberately vague on how it originated.

Reliable French and diplomatic sources now report that Poniatowski was alerted by the counterspionage agents who handled the case of Abu Daoud's presence in Paris, and that he personally made the decision without taking it up with Giscard, who was away for the weekend.

Poniatowski is one of the few ruling French politicians who has often been described by Israelis as "a friend of Israel" because of his sympathetic attitude toward the Zionist cause. But it appears that the Abu Daoud arrest stems more from a serious miscalculation by Poniatowski than a desire to please Israel.

He evidently felt that the Palestinian movement had been seriously weakened by the Lebanese civil war and that conservative Arab governments like Saudi Arabia would be pleased to see a terror leader under arrest. He also thought that West Germany, which had a warrant outstanding for Abu Daoud, would move quickly to take him off French hands.

But Arab ambassadors put up a loud howl, the Germans moved slowly and the French government decided to find ways to let Abu Daoud go free quickly.

The still unraveling Prince de Broglie murder case is a potentially far more troublesome affairs domestically. De Broglie was shot down in a Paris street on Christmas Eve by a hired killer for motives that remain obscure.

The talkative gunman told investigators that he had been hired for the job by a policeman who was acting for "big guys who would cover us."

Poniatowski called a press conference five days after the murder to announce that "everyone involved in the murder has been arrested." According to the police version presented at the press conference the crooked policeman had been hired by two low-level underworld figures who owed De Broglie $800,000 and wanted to eliminate the debt.

De Broglie a member of the National Assembly one of the two top French negotiators who arranged Algeria's Independence and a member of Giscard's party, lent them the money to buy a restaurant and the two men could not keep up the payments, according to the police.

French news magazines quickly surfaced copies of the loan agreement that showed that the debt still had to be paid even if De Broglie died. The two prime suspects were, in fact, in worse financial shape because of his death.

More of the police version has come unstuck as details of De Broglie's far-from-spotless personal and business lives emerge. He helped front more than 40 companies, many set up in Luxembourg, which dealth in oil, arms and other high-profit ventures.

Some of the documents under investigation have been inadvertently burned by police when being photocopied, and the prince's chateau was broken into by expert burglars looking for papers. Each new witness or lawyer involved in the case adds to the impression that the upper level of a French underworld that has important political friends is involved in the case.

"It is like starting a murder mystery at the end and having to work your way back," one of the French journalists investigating the case said shortly after it began. "We don't know where it will go, but we are alreadly far from that restaurant that was Mr. Poniatowski's answer to the whole thing."