Supporters call it "the Spirit of 13," after the famous ballot proposition that stood California's tax structure on its head. Others think of it as the slow-to-grow child of an unsuccessful government spending limitation sponsored by then-Gov. Ronald Reagan six years ago. A few say it is a fiscal time bomb disguised as a motherhood issue, waiting to go off if the nation's most populous state has a serious recession.

It is Proposition 4, a complex state constitutional amendment designed to clamp a permanent lid on state and local government spending. Voters will find it on the Nov. 6 ballot.

In scope and intention, Proposition 4 goes beyond government spending limits such as those enacted in Tennessee, Michigan, Texas and Arizona. It would fix state and local spending at 1978-79 levels, adjusted for inflation and population growth Budget surpluses would be returned through lower tax and fee schedules. The state treasury would be required to come to the aid of local governments if the legislature in Sacramento mandates new programs or requires higher levels of service.

Proposition 4 is the brainchild of Paul Gann, the lesser-known partner of the political team that rocked the nation in 1978 with the state property tax-limitation measure known as Proposition 13.

Proposition 13 made fast-talking Howard Jarvis famous and launched him on an internation career as an antitax promoter and consultant. It left the soft-spoken Gann back home in Sacramento, convinced that only the first step had been taken in his long crusade to control the cost of state government.

Where Jarvis is California flamboyant Gann is California mellow. Jarvis is loud-talking, profane and relentless in debate, a veteran politician who has made no secret of his liking for good food and drink and who revels in his acquired image as a middle-class American folk hero.

Gann is tee-totaling, white-haired and short, no more noticeable in a crowd than any other retired 67-year-old grandfather. He is the son of an Arkansas-born Methodist minister and his speeches are sprinkled with homilies about the virtues of public service and hard work.

Jarvis and Proposition 13 were attention-getters, attracting controversy as readily as Gov. Edmund G. (Jerry) Brown Jr. draws television cameras. In contrast, Gann and Proposition 4 have gone almost unnoticed since a $537,000 signature campaign qualified the initiative for the ballot.

Noticed or not, the consensus prediction is that Proposition 4 will win in a walk. A survey by veteran pollster Mervin D. Field in mid-September showed the initiative leading 61 to 28 percent, with 11 percent undecided. A private poll taken early this month in San Diego put Proposition 4 ahead by a 5 1/2 point margin.

While Proposition 13 was denounced by liberal, labor and minority group leaders, organized opposition to Proposition 4 is negligible. The measure has the backing of the state's major business organizations and also of liberal Democrats; like Assembly Speaker Leo. T. McCarthy who appear to be searching for opportunities to demonstrate fiscal conservatism.

Surprisingly, the only politcian of consequence who has failed to endorse Proposition 4 is Gov. Brown, but he is expected to do so soon. Brown, who has predicted a severe recession, said in a telephone interview this week that he favors a constitutional spending limit in principle but wants his finance department to make an analysis of the proposition before he supports it publicly.

On its face, Proposition 4 appears to be a liberal dream of a measure that sounds conservative but would have no immediate adverse impact on government spending. Jonathan Lewis, executive director of the California Tax Reform Association, scoffs at Proposition 4 as "a fraud" on shot through with loopholes. But the California Taxpayers Association, a group that favors Proposition 4, argues that without Proposition 4 government spending could increase 22 percent over the next two years; it bases its estimate on current growth and population and the U.s. consumer price index.

But one provision of Proposition 4 would require local governments to use-California's per capita personal income figures rather than the price index in their growth computation if personal income is lower. Gann observes that personal income was lower than the index at four points during the past decade; this would be the case again, he says, if a major recession hits the California economy.

In such an event, local governments might find themselves unable to maintain present levels of services for the state's growing population.

Gann dismisses the doomsday predictions, pointing out that his measure, unlike Proposition 13, permits higher levels of spending by a vote of the people.

And if the politicians can't persuade the people to vote additonal spending, says Gann, that's their problem.

"The politicians have been assuming they have the divine right to do anything they want," Gann says in this characteristically quiet voice. "They don't have that right. They're not deities, just people.