Prime Minister Indira Gandhi's remaining son, Rajiv, once content to be free of the life of political intrigue that surrounds his family, is now being drafted into public life. But he is coming reluctantly and without ambition.

The hopes of the prime minister's supporters that a Gandhi dynasty would endure were dimmed in June when Gandhi's younger son, Sanjay, was killed in an airplane crash.

Sanjay was his mother's political heir apparent and loved the role. He was probably the only person she truly trusted, confided in, and leaned on. She was grooming him for succession, just as her father, India's first prime minister, Jawaharial Nehru, groomed her.

Now she is looking for support from her other son, even though he has not been interested in politics before. He was happy as a pilot with Indian Airlines, flying twin-engine Avros. Even in his preflight announcements, he downplayed his notoriety and announced himself as "Captain Rajiv" not "Captain Gandhi."

Among a small circle of friends, he was enthusiastic about flying and stereo sets. If the talks turned to politics, Rajiv would usually become bored and seldom joined in. However, it was known that he did not care for his brother's controversial work during India Gandhi's 17-month emergency rule. Sanjay's pursuit of forced sterilizations is credited with greatly raising the opposition to his mother that in 1977 forced her from office for nearly three years.

One informed source said that Rajiv's few comments about his brother's work were "disobliging."

Rajiv's next step is uncertain. At the time of his brother's death, he was scheduled to begin training for Boeing 737 jets. He has since turned that offer down and is on leave. Political observers expect tht he will soon enter politics.

"Tajiv still doesn't seem to have political ambition," one Western source said. "He is going to be a good son to his mother. She wants him there, and he will come. I don't see him being more than an emotional and psychological prop to her."

In two separate interviews with Indian magazines Rajiv said he has not yet made up his mind but would prefer not to get involved in politics.

He said he would rather act as a personal assistant to his mother, screening her visitors because "she cannot possilby meet everybody," and reporting to her what people think and what their problems are.

Rajiv told the magazine India Today that his Italian wife Sonia was "dead against the idea" of his entering politics and he said his mother has not directly asked him to do so. Pointing out that Sanjay had been "in the game" since 1973, Rajiv said he could not give his mother the sort of support Sanjay had been providing.

An Indian commentator, writing in a national newspaper, commiserated with Rajiv.

"To be surrounded by all manner of time-serving toadies and told that you have suddenly become a white hope of the country is an experience any man of normal instincts must find distasteful," he wrote. "Still, having gone through it, Rajiv at least has some idea now of the perfidious world of Indian politics he is entering."

Nonetheless, Rajiv might find that he may develop a taste for power after all, as his mother seems to hope. Or he could simply embrace the responsibility and grow into the job.

Some Indian sources are uneasy about the future of Gandhi's ruling Congress-I (for Indira) Party. They are anxious about Gandhi's successor since they are worried about her health without the prime minister, they fear, the party would collapse.

Gandhi has been scarred by her tumultuous life and she is looking haggard and ill. She is compared to a brittle stick, hard and unbending. Her composure in the grueling days following Sanjay's death awed many Indians. But for all that, she is not invulnerable, and many are watching her with concern.

It seems unlikely that Rajiv will emulate his brother and observers here also are watching him to see if he can fill the void in the party leadership created by his brother's death.

When he died, Sanjay was busily moving his own Young Congress nominees into crucial government and party slots, but he had not yet reached the stage of using them. Now they are in place but uneasy because the leader from whom they derived their authority is gone.

Many of the Oung Congress officials are clearly hoping to manipulate Rajiv, and most of them, as well as senior party members, have been trying to attach themselves to Rajiv's rising star.

Gandhi may well need Rajiv's help soon, for despite all the work she puts into her job, there is little to show for it at the end. In the eight months since she resumed power, hers has been an extraordianary administration.

"The government that works" -- according to its election promise -- has seemed almost totally inactive. The great challenges facing the nation on every front -- prices, crime, unrest in the northeast, atrocities against untouchables, bloody clashes between Hindus and Moslems -- have not been confronted.

Even her Cabinet remains unfilled, despite three expansions and reportedly there is a reshuffle pending. There is no minister of defense and Gandhi is handling that portfolio temporarily. She also had no industry minister, no minister of labor, no minister of health.