An anti-smoking initiative that its advocates hope will start a national trend apparently is falling victim to the well-aimed salvos of the tobacco industry.

The state constitutional initiative, Proposition 5 on the November ballot, would ban or severely restrict smoking in most public places. Proposition 5 led by a wide margin in early public opinion polls but now has fallen behind, largely as the result of an expensive and imaginative advertising campaign which suggests that the initiative violates free speech, common sense, and the American aversion to government regulation.

Because California is a trend-setting state with a tenth of the nation's population, the tobacco industry regards the initiative as potentially the most dangerous threat since the U.S. Surgeon General warned 14 years ago that smoking could be a serious health hazard.

Reported expenditures against the initiative, most of them from cigarette companies, already top $3 million. The spending total could reach $5 million by the end of the campaign - expensive even by California standards.

The opponents have been aided by some inept draftsmanship which exempted rock concerts from the restrictions of Proposition 5. The reason given for the exemption is that many people smoke marijuana cigarettes at rock concerts and that enforcement of the marijuana laws is difficult.

This has helped the opponents make one of their major arguments, which is that Proposition 5 either would be unenforceable like prohibition, or would consume resources that police agencies should devote to more serious crimes.

The later arguments is widely accepted among law enforcement agencies, a number of which are struggling with cutbacks prompted by Proposition 13. Many California sheriffs and several police chiefs openly are opposing Proposition 5.

Polls taken by the Los Angeles Times and the Sacramento Bee indicates that Proposition 5 is now losing after leading in summer surveys. The state's bestknown poll, the California Poll of Mervin Field, earlier this month showed the proposal tied after it had led 58 to 38 percent in a late August poll.

"When you have this kind of movement on ballot propositions, they lose 9 out of 10 times," says Fields.

But the tobacco industry isn't taking any chances.

"We're not chilling the campaign yet," says Jack McDowell, partner in the San Francisco advertising firm which is de-Franciso advertising firm which is managing the No-on-5 campaign.

McDowell believes that the issue is very close, and says that advertising against the initiative will continue unabated until the polls close.

The proponents, supported by medical groups, the American Cancer Society and the California PTA, will spend an estimated $500,000 to pass the initiative. But they are also getting free time from nine television channels and 17 radio stations which are making an effort to balance the competing arguments.

The proponents have obtained a string of endorsements from celebrities, among them Gregory Peck, Charlton Heston, Carol Burnett, Lena Horne, and John Forsythe.

"You can't put a price tag on life but big tobacco companies are trying to do just that with a series of clever commercials that ask us to vote against Proposition 5," says the Forsythe radio commercials. "They say it will cost too much. Baloney. The legislative analyst says it will cost Californians about 4 cents each, if that, but it can also save pain and life."

The 4 cents mentioned by Forsythe is an estimate of the $20 million statewide cost of living posting no-smoking signs in public places, a tab the American Cancer Society recently announced it would pick up. Opponents say the cost will top $260 million because of the remodeling that businesses will be forced to make if they decide to provide separate smoking and non-smoking sections for their employes.

But the most effective arguments of the opponents probably is a television commercial featuring a barber who decries the intiative as an invasion of free speech. It ends up with a customer asking: "What will they regulate next.?"

Not, apparently, smoking in public places in California.