More than 200 million Indian voters are expected to go to the polls Monday as parliamentary elections start in the world's largest democracy amid signs that Prime Minister Rajiv Gandhi may lead his ruling Congress (I) Party to one of the biggest majorities since India won independence.

The 40-year-old heir to the Nehru dynasty was thrust reluctantly into the leadership of 750 million Indians by the assassination of his mother, Indira Gandhi, on Oct. 31.

But with a political apprenticeship of only three years, he has inspired, in just two months, a mandate for political reform that nationwide opinion polls forecast will win his party nearly three-fourths of the 511 seats being contested for the Lok Sabha, or governing house of Parliament. Elections in the strife-torn states of Punjab and Assam have been postponed for security reasons.

In the nearly unanimous view of political analysts, Gandhi will fare far better than his mother, had she lived to face her fifth national election, partly because many people who would have voted against her in their desire for change will vote for him for the same reason.

Congress (I), which already holds a comfortable majority of 355 seats in the 544-seat Lok Sabha, stands to win 366 of the 511 seats being contested next week, according to a nationwide opinion poll conducted by the Marketing and Research Group for the magazine India Today. With its allies, Congress (I) could command more than 400 seats in the next session of Parliament.

Because of the enormous problems of providing security and poll monitoring at 480,000 voting stations across the Subcontinent, balloting will be held on three days -- Monday, Thursday and Friday -- with results likely Friday night.

When he announced the elections on Nov. 13, the day after official mourning for his mother ended, Rajiv Gandhi appeared ready to benefit from little more than a wave of sympathy arising out of the assassination, although the sympathy factor was a formidable one for a fragmented and quarrelsome opposition that had not even decided who would lead a coalition government should the Congress (I) be thrown out of power.

Emerging from near-obscurity as a former airline pilot and new member of Parliament, Gandhi immediately gained widespread recognition for his composure and strength during the funeral ceremonies. The rites were beamed to millions of television viewers over a vastly expanded network that had been rushed to completion by his mother's administration in anticipation of her election campaign.

Gandhi benefited further from his decision not to postpone the election, and also from a strong policy address in which he pledged to lead a reformist movement toward a "more goal-oriented" government with less corruption.

Moreover, by personally taking charge of the selection of candidates for his party's parliamentary tickets -- and by dropping a number of members or prospective candidates widely associated with corruption or political stultification -- Gandhi enhanced the aura of reform that gradually was building around him.

One leading political analyst here who initially watched this early development with skepticism, Pran Chopra of the Center for Policy Research, said he gradually became impressed with Gandhi's ability to transcend the sympathy factor that might alone have won him a comfortable majority, and to capitalize on a yearning for change among much of the electorate.

"There is no doubt that the end of Mrs. Gandhi's prime ministership caused a sense of relief among some people who felt that politics under her was too tense, too crisis-ridden. A rather oppressive sense of tension abated after the assassination, followed by a feeling that change may be afoot," Chopra said.

Besides the sympathy for Indira Gandhi, he said, there was a growing expectation that at hand was a leader without her domineering sense of power and manipulative skill -- one who had been flying Indian Airlines planes during the 1975-77 emergency period and was not tainted by that oppressive era or encumbered by the dislike of what were perceived as his mother's confrontationist and divisive policies.

Consequently, Rajiv Gandhi became the hope not only of those who wanted a continuation of Indira Gandhi's strong leadership, but also of those who wanted a reversal of her policies.

The catalyst for what is now being widely anticipated as "Rajiv's mandate for change" was provided in part by the sectarian upheaval that followed his mother's assassination by two Sikh security guards, resulting in the deaths of about 1,500 Sikhs at the hands of Hindu mobs.

Rather than attempting solely to exploit a Hindu backlash in the vote-heavy "Hindi heartland" that stretches across five northern states, Gandhi has campaigned extensively in other regions of the country on a theme of national unity.

Opinion polls show that Gandhi's support in the Hindi-speaking states has been nearly equaled by his support in the rest of the country. If the polls hold up, Gandhi will have an even broader geographic mandate than his mother won in the 1980 election.

In surveys, nearly half of the eligible voters questioned said they considered national unity the most important issue; only about 30 percent listed inflation. Corruption in government was a distant third, with about 15 percent.

"He's making patriotism his own personal issue, and it's a difficult thing to counter," said Ramakrishna Hegde, Janata Party leader in Karnataka State and one of the strongest national opposition figures in India.

Gandhi's campaign swing through Haryana Thursday typified the style that he has developed to benefit from the dominant issue of national unity in the face of foreign and domestic threats to India.

Traveling by Air Force helicopter, he hopscotched the state at a frenetic pace, dropping in at huge public rallies and sounding a recurring theme in 10-minute stock speeches.

"Indira Gandhi said three months ago that people from other countries would try to sabotage our country. We didn't listen to her, and on Oct. 31 they killed her," he told more than 100,000 people at a soccer stadium in Gurgaon. He did not specify what "other countries" he meant but implied involvement by Sikh separatists based abroad and supported by India's traditional antagonist, Pakistan.

"Is the Khalistan Sikh separatist movement supported by the opposition parties in India or not? We must be aware of these people on Dec. 24 and remove them from politics," Gandhi said, insisting that only his party could ensure the continuity of the Indian union because the opposition lacked unity.

Similarly, in a speech in New Delhi today, Gandhi said the time had come for voters to choose between a party committed to the unity of India or "forces of destabilization and disunity.