Approval of a proposed constitutional amendment on the November ballot that would allow the state to spend public funds on private preschool programs is uncertain as support for the initiative continues to wane and opposition has mounted in recent months, according to new Hawaii Poll results.

Fifty percent of voters interviewed this month said they would support the preschool amendment, while 42 percent said they would vote against it. Seven percent were undecided.

Constitutional amendments need a majority of yes votes — 50 percent plus one vote — among all ballots cast in order to pass, meaning blank and spoiled votes have the same effect as "no" votes.

Support for the initiative was highest among voters under age 35 and those earning less than $50,000 a year, according to the poll conducted Oct. 11 to 18 by Ward Research among 605 likely voters statewide. The margin of error is plus or minus 4 percentage points.

Support has dropped off from 62 percent of voters in a February Hawaii Poll, and from 54 percent in favor in a Hawaii Poll taken in July. Meanwhile, those saying they would vote against the initiative grew from 33 percent in February and 40 percent in July.

The state Constitution prohibits public funds from supporting or benefiting any private educational institution.

The amendment, if approved, would give the state the ability to use a combination of public preschool classrooms at public schools and state-funded slots in private preschools to eventually serve all of the state’s 17,200 4-year-olds with a publicly funded preschool education.

Early-education supporters say a mixed-delivery system is the most cost-effective route to expand capacity and serve more keiki.

But the Hawaii State Teachers Association, representing some 12,500 public school teachers, strongly opposes the amendment, arguing that preschool programs should be available to all children, free of charge, at public schools.

"We don’t want to leave any child behind," HSTA President Wil Okabe said. "Education, for us, that’s our profession. Our teachers are leaders in education, so we have to advocate for the best educational opportunities for all children because we believe all children should have equal access."

Okabe said the union has been encouraging its members to let their families and friends know about their stance on the issue.

"We support universal preschool, but we cannot support a constitutional amendment that doesn’t have laid-out plans in place," he said. "We’re going to give it every effort until the fourth quarter, and hopefully we can score a touchdown on Nov. 4."

In contrast, the Good Beginnings Alliance, a nonprofit early-learning advocate, is urging voters to support the initiative, arguing that the move will make preschool more widely available for families, especially low-income families.

"We know it will be close and that it’s challenging to pass a constitutional amendment, but we’re hopeful," Good Beginnings Alliance Executive Director Debo­rah Zysman said. "That’s in the face of HSTA trying to confuse and trying to raise questions. What we’re trying to say is there’s actually a lot of answers, there is a plan on the table. The Legislature has debated this repeatedly. We don’t need to discuss this for 20 more years. We need to do something and we need to start now."

Hawaii is one of 10 states without state-funded universal preschool. Half of the state’s 3- and 4-year-olds enter kindergarten without a preschool education, which on average costs about $800 a month at private early-learning centers.

If a publicly funded mixed-delivery program is created, private preschools that choose to participate in the state’s early learning program would have to abide by contract terms that would include quality indicators such as educational outcomes for students, according to the state Executive Office on Early Learning.

Receiving state funds also would mean that participating preschools could not discriminate on their admission policies using requirements such as ability (testing to get in, for example) or religion.

If the amendment fails, officials say the state will only be able to work within the Department of Education to create state-funded preschool classrooms.

The Executive Office on Early Learning has estimated that a full-scale, mixed-delivery system serving 85 percent of the state’s 4-year-olds would cost an estimated $125 million a year to operate, with about $48 million of that coming from the state and the rest funded by a combination of federal, parent and private foundation funds.

Running a purely public pre-kindergarten system within the DOE has been estimated at a cost of $150 million a year, not including infrastructure costs to add classrooms.