SAN FRANCISCO – Actor-director Rob Reiner’s campaign to tax the rich to offer free, state-funded preschool to every 4-year-old in California is encountering some resistance from unexpected quarters.

The universal preschool ballot measure, scheduled to go before voters in June, has long been considered a sure winner. Now, its prospects seem less assured after a key backer of the “Preschool for All” drive withdrew support and Mr. Reiner came under fire for sitting on a state board that spent $23 million in taxpayer funds on television ads promoting the idea.

For proponents of the initiative, the most worrisome development may be the defection last week of one of the California Legislature’s liberal leaders, the president pro tem of the California Senate, Don Perata.

An aide to Mr. Perata said on Friday that he was recovering from a back injury and unavailable for an interview. Earlier, the lawmaker told the Sacramento Bee that he changed his mind about the preschool measure after examining it in detail.

“There are some flaws there that are, I think, fatal,” Mr. Perata said, a Democrat who represents Oakland. “There’s no means test. And so it looks to me like it would be really a boon for middle- to upper-middle-class families.”

Mr. Perata also said that while the initiative is silent about whether the new services should be delivered by public schools, private companies, or nonprofit community groups, public employee unions are likely to demand that their members staff the preschools.

“There will be great pressure on the county superintendents to use school districts. I think county employees will provide that pressure. So, that’s another flaw,” the lawmaker told the newspaper.

Asked why he endorsed the initiative last year, Mr. Perata said, “I was sort of caught up in the need and the value of preschool.”

The initiative drive also has been stung by reports that a state board that promotes early childhood programs, the First 5 Children and Families Commission, spent $23 million in recent months on ads that touted the value of universal preschool. Mr. Reiner is chairman of the commission, which was created after voters approved a ballot measure the actor sponsored in 1988, adding a 50-cent-a-pack tax on cigarettes.

On Friday, Mr. Reiner took leave from his commission post after lawmakers from both parties called for an audit of the board and questioned whether its expenditures may have violated California law by seeking to sway public opinion about the new initiative.

A spokesman for Mr. Reiner, Nathan James, declined to discuss the controversy over the ad campaign and said Mr. Reiner was not available for an interview.

“The initiative is backed by more folks than just Rob,” Mr. James said. He noted that the measure has been endorsed by the California Teachers Association and by local chambers of commerce in Los Angeles, Oakland, and San Francisco. A January poll found 63% of likely voters in favor of the measure.

One of the leading talking points for backers of the initiative has been a study, conducted by the RAND Corporation, whose researchers found that funding universal preschool would provide long-term benefits that more than covered its costs.

The Preschool for All Web site contends that the RAND study determined that each dollar spent on preschool education would produce “$2.62 in savings from reduced remedial education, lower drop out rates, less crime and a better educated workforce.”

That language could lead some voters to conclude that the state would see the bulk of the payoff from preschool spending. In fact, about two-thirds of the financial benefit from the program would go to the families of the enrolled preschoolers and to the children themselves, according to an author of the study, James Bigelow.

“There is a net payoff for society as a whole. That doesn’t mean there is a net payoff for the government,” Mr. Bigelow told The New York Sun.

Anti-tax groups and some business organizations have opposed the preschool initiative, which would raise between $2 billion and $2.4 billion a year by hiking the top state income tax rate to 12%. The change, which affects couples who make more than $800,000 and individuals who make more than $400,000, would give California the highest state income tax rate in the nation.

Mr. James described the arguments against the initiative as a “smokescreen” for the true agenda of its critics. “It’s an attempt by opponents of the initiative to kind of distract from their real concern, which is they’re opposed to any kind of tax increase for education.”

Mr. James said he was “not at all” concerned that Mr. Perata’s defection could herald a wave of liberal opposition that could doom the initiative. “Don Perata can be part of the solution or part of the problem,” Mr. James said.

One education professor who supports more government spending on early childhood education said yesterday that Mr. Perata is on target with his critique of the initiative. “It’s subsidizing people who are already in it,” Russell Rumberger of the University of California at Santa Barbara said.

Mr. Rumberger recently completed a study showing preschool has limited but significant benefits for children, but he said politics is driving the current initiative. “Politically, it’s more likely to be sold as a middle class benefit. In this day and age, we can’t channel scarce resources to do that,” he said, adding the state would be better advised to get all poor kids into preschool at age 3.

A review of the initiative by a libertarian think tank, the Reason Foundation, produced the eye-popping claim that the new program would cost $109,000 for every new student placed in preschool. The high cost comes from the fact that about 65% of American 4-year-olds already get some care outside the home. Backers of the universal preschool program, which would be voluntary, say it would probably enroll about 70% of children.

“It’s a very expensive way to provide preschool,” the foundation’s director of education policy, Lisa Snell, said.

Ms. Snell said the initiative’s requirement that every preschool classroom include a teacher with a bachelor’s degree and teacher training would lead to an exodus of current day-care providers, who are often less educated. “Generally, it’s not a liberal position to come out in favor of a program that will make low-income women lose their jobs, particularly low-income minority women.”

Mr. James said the Reason analysis is faulty because the number of 4-year-olds in “quality preschool” is closer to 25%. The 65% figure includes all kinds of other arrangements. “It could be baby-sitting or throwing a kid in front of a TV set,” he said. The teacher requirements would be phased in, and the initiative includes scholarship money to help current day-care workers, he noted.

While critics of the California universal preschool initiative warn that its passage could prompt similar efforts in other states, New York actually committed to the idea nearly a decade ago.

“We, I think, have crossed that decision point,” the coordinator of New York’s universal preschool program, Cindy Gallagher, said in an interview last week. Ms. Gallagher, who works for the state Department of Education, said that in 1997, New York’s Legislature passed a bill aimed at phasing in universal preschool, or “pre-K,” over a four-year period.

However, the program was never fully funded, in part because of a budget crunch that followed the September 11, 2001 terrorist attacks, she said.

At the moment, about 25% of four-year-olds in New York attend state-funded preschool, Ms. Gallagher said. Several other states have set goals for universal preschool attendance, but only a couple, Georgia and Oklahoma, have fully implemented their programs.

Ms. Gallagher said she doesn’t see the program as a windfall for middleclass parents because costs of preschool and day care have risen even as New York has increased its subsidies. “I don’t think parents have seen that much reduction,” she said.

Ms. Gallagher said she and her colleagues are closely following the “strong debate” in California over the initiative. “We really see pre-K in terms of research and in terms of our experience, that it is a key strategy for closing the achievement gap in students. We want it to be part of a public school continuum.”