A normally quiet election for a largely unknown Harvard University governing body has emerged at the center of a long-running debate over whether the nation's richest college should divest its interest in firms that do business in South Africa.

The mail ballot to 160,000 Harvard alumni to elect five members to the Harvard Board of Overseers, a largely advisory body that serves as a companion to the more powerful Harvard Corporation, has been tinged this year with allegations that Harvard has tried to influence the outcome to preserve its anti-divestment stance.

"Any way you slice it, the election is now a tainted election," said John Plotz, a San Francisco public defender running as one of three antiapartheid candidates.

The controversy on the campus of one of the nation's oldest and most prestigious universities has prompted a flood of letters from outraged alumni and full-page advertisements in the Harvard Crimson newspaper. It has also created embarrassment for the school as it prepares to celebrate its 350th anniversary with festivities planned for later this year.

The controversy began when the Alumni Against Apartheid group nominated three candidates for five open seats on the 30-member board. The pro-divestment slate was endorsed by South African Bishop Desmond Tutu.

The current board president, Joan Bok, sent a letter along with the ballots essentially warning graduates that "In 1986, for the first time in my recollection, three alumni are actively campaigning as petition candidates in order to press a specific issue, the total divestment by Harvard University . . . . "

The letter from Bok, who is no relation to Harvard president Derek Bok, did not directly urge the graduates to vote against the three divestment candidates. But it did say: "If the Board of Overseers were to become a body made up of members elected primarily to press a particular policy, it would be a very different board than it has been heretofore."

Her letter was accompanied in the ballots by a statement of Harvard's official position against divestment, and a separate letter from the chairman of the alumni association.

The three divestment candidates later asked that they be allowed to mail out their pro-divestment literature at school expense but were refused.