A controversial Dade County antismoking proposal apparently lost by a narrow margin tonight in what a county election official called a "cliffhanger."

Final returns showed that the proposed ordinance to restrict smoking in many public places received 93,871 votes, with 95,074 votes against it.

The official, Jody Gluck, assistant supervisor of elections, said the outcome would not be decided officially until Wednesday, when the canvassing board counts 3,278 absentee ballots. But she added, "Historically, the absentee ballots reflect the precinct count and do not change a race. But there is a first . . . time, and it is possible."

Only 27.4 percent of the electorate of 702,000 went to the polls in this referendum, which was the only issue on the ballot in most of the county.

It was the first major test of the smoking issue since a similar proposal was defeated in California last November.

Foes of the measure, organized as Dade Voters for Free Choice, raised more than $960,000. They waged a newspaper and television ad campaign based on the theme "Don't let it happen here."

At least two-thirds of the group's funds came from tobacco companies, with R. J. Reynolds contributing the most, $360,000.

The pro-ordinance Group Against Smokers' Pollution (GASP) reported raising about $8,000. It relied mainly on news coverage to spread its message, which depicted tobacco smoke in enclosed areas as harmful to the "health, welfare, comfort and environment" of nonsmokers.

The so-called Clean Indoor Air ordinance got on the ballot after GASP obtained 10,000 signatures on petitions. The ordinance would limit smoking in most "enclosed public places, places of employment, educational facilities and health facilities." Separate smoking and nonsmoking areas would have to be designated in such places. In restaurants, for example, at least half of the seats would have to be set aside for nonsmokers. Bars, tobacco stores, hotel guest rooms, pool halls and certain other establishments would not be affected.

Private residences also would not be covered, nor would "any fully enclosed office or room occupied exclusively by smokers who generally do not meet with members of the public in such office or room," according to the ordinance.

Violators would he subject to fines of up to $500.

Opponents argued that the measure would be unenforceable and expensive for government and businesses to comply with. They claimed that the cost of signs, partitions and management time would be $8 million. Antismokers argued that the cost of treating people for smoke-induced diseases is far greater.

Proponents said Dade County's 1,300,000 residents spend $300 million in health care and that 2,500 lose their lives each year because of smoking-related illnesses.

Dade County - which includes Miami, several large suburbs and some rural communities - already has ordinances curbing smoking in such places as buses, elevators, department stores and retail food stores.

In New York, meanwhile, the state Assembly voted Monday to ban smoking in most public places, except for special areas. The bill now goes to the Senate. CAPTION: Picture, Max Kaplan, 80, a clerk at a Miami Beach polling place, enjoys a cigarette as he tends ballot box. AP