A decade ago, when Morarji Desai fought Indira Gandhi for leadership of India's Congress Party, he made it plain that he considered himself infinitely better qualified than what he called a "mere schoolgirl."

Now that Gandhi and her party have gone down to defeat, the austere and mission-bosessed Desai, at 81, has a chance to prove what he can do after years of trying to become prime minister. Power came to him so late in life largely because he is one of those politicians, hovering between greatness and crankiness, who have a special gift for alienating their colleagues.

Even his personal appearance - tall, straight-backed and soldierly, with short-cropped hair - suggests the total personal certainly and self-confidence theat win him both admiration and enemies.

"I have no will," he says, "I am only God's instrument" - and then has adds that he belongs to the tiniest of all human minorities, those who are inherently moral.

Desal's views on clean living are very much a part of his politics, and some government officials have expressed the fear that he might ersume his party successful drive to halt the spread of air conditioning in government offices.

"That Desai," growled one high-ranking official as he sat under a ceiling fan. "If it weren't for him this building would be air-conditioned."

Desai himself follows a strict vegetarian diet, drinks no alcohol, does not smoke and says he renounced sex in 1928.

Although some reports say he has eased up on his long campaign against alcohol, many doubtful jourstockpiling liquor in case Desai won.

He begins each day with yoga exercises and prayer, and tries to spin at least a few yards of yarn on a spinning wheel every afternoon - one of the few Indian politicians who still follow Mahatma Gandhi's prescriptions on this. Naturally, he wears only white homespun garments.

But his puritanism is of the elegant variety: His homespun is of the very finest quality, and his frugal meals are made up of choice fruit and the freshest of milk sweetened with clear honey. Often he takes several squares of good Swiss chocolate as dessert.

A civil servant, a veteran of the freedom movement and one of the best of the Congress Party's leaders. Desai was an already established figure by 1956, when he came to New Delhi.

In 1964, when Jawaharlal Nehru died, Desai and Lal Bahadur Shastri were the main contenders to succeed him, but Desai's inflexibility and his certainty that he was a better and more moral man than the rest - including Nehru himself - spoiled his chances and he was forced to withdraw.

After Shastri died, Desai forced a contest with Nehru's daughtre, Indira Gandhi, and lost decisively in a party struggle.

Again in 1967, when poor election results had weakened her position, he moved against, but was forced to accept a compromise in which she stayed on as prime minister and deputy prime minister.

For a fourth time, in 1969, Desai - allied with some of his earlier rivals - tried to force Indira Gandhi out, and the Congress Party split. The majority stuck with Gandhi, and Desai and his allies were left with what was known as the Opposition Congress Party.

His fifth and final attempt for power can be said to have begun in 1974, when he led an anti-corruption drive in Gujarat, his home state, similar to that Jayaprakash Narayan was carrying on in Bihar. These campaigns led, via a court decision convicting Mrs. Gandhi of election-law violations, to her declaration of a state of emergency and, eventually, to her downfall.

Under the emergency rule, Desai spent 18 months in jail, but he says he bears no ill will toward Indira Gandhi, calling her "a spoiled girl." Still, he appears determined to press for investigations of scandals involving her and her son Sanjay.

Indians see Desai as cold, but he has a lighter side; while he reads mainly Hindu religious books, he also enjoys "short stories, if there are any to hand," he adds: "A man can't live without a sense of humor. Mine is improving all the time."

His simple egoism underlies his calm statement that Mahatma Gandhi was not his mentor - that the two men are equals who happened to have arrived at the same ideas.

Like almost every politician in India, he calls himself a socialist, but in office he has generally encouraged free enterprise and the investment of foreign private capital. He dislikes Communists and is wary of all those, such as Jayaprakash Narayan, ever associated with the party.

"A poor man," Desai says, "has more virtues than a rich man. Domestic servants, for instance, rarely steal. Yet the rich live by felony. How else but by felony does a man become rich?"

Clearly more moralist than modern politician, Desai has aroused some fears that his tendency to be rigid and simplistic could provoke a sharp reaction.

Still, India does need some form of moral renewal, and Desai may be able to provide it. As chief minister of Bombay, he imposed prohibition and tried to drape the city's nude statues - but he also prosecuted nearly a thousand police officers for corruption and mistreating the public.