Reaching the voters: TV, billboards, and above all, personal appearances

There are 390 million of them, spread from the northern Himalayas to the sun-baked villages of the south. Although nearly 7 out of 10 are illiterate, and more than half live below the poverty line, the voters of India pride themselves on the power they wield in sustaining their nation's democracy. In no election since 1957 has voter turnout been below 50 percent.

They want to see their candidates, to apply a discriminating eye. Thus, Prime Minister Rajiv Gandhi did not heed his advisers when they urged him to limit his personal appearances in favor of television because of the risk of an attack on his life. On the contrary, in his election kickoff tour, he visited as many as 17 towns, cities, and villages a day, traveling more than 5,000 miles in four 16 -hour days. The schedule took him to seven of India's 22 states.

This is Rajiv Gandhi's election - planned, charted, and programmed, even before his mother's death, by what many Indians derisively call the ''computer boys'' who make up his inner entourage. They are former management executives, and before that, Mr. Gandhi's former classmates from the prestigious Doon School.

This will be India's first television election. The installation of 165 transmitters throughout the nation has the potential of bringing Gandhi and other party leaders to 70 percent of the electorate through communal TV sets.

It is also the first election in which the ruling Congress Party has hired a major advertising agency.

Half-page newspaper ads directed at the educated elite have concentrated on the party's message of national unity. The ads were meant to be subtle and discreet, but they are so discreet that many New Delhi intellectuals have had difficulty understanding them.

Thus, canvassing, graphic billboards and flyers, and video shows in the villages have remained supreme - as in India's seven previous elections.

But the sheer expanse of this nation - 2 million square miles, where 515 members of Parliament's lower house will be elected by votes cast in 1.5 million ballot boxes in 430,000 polling booths - has made each election increasingly expensive.

Some say the costs are prohibitive for a nation whose per-capita gross national product is only $260 a year.

(Elections are not being held in violence-wracked Assam and Punjab States, whose 27 seats will go unfilled.)

Estimating that the election will cost $175 million, D. H. Pai Panandiker writes in the Hindustan Times that the expenditure translates into 0.13 percent of the national income.

Asks the secretary-general of the Federation of Indian Chambers of Commerce and Industry somewhat plaintively:

''Why should a poor country spend more on democracy?''