Early learning advocate The Good Beginnings Alliance has spent more than a half-million dollars on television ads to lobby support for a proposed constitutional amendment that would allow spending public funds on private preschool programs, according to the latest round of campaign-finance reports.

The nonprofit formed a so-called ballot issue committee — which is not subject to contribution limits — that has largely been funded by donations from Kamehameha Schools and philanthropists Pierre and Pam Omidyar.

Kamehameha Schools, which operates 30 preschools statewide, donated $500,000 to the cause, while the Omidyar Family Trust chipped in $350,000.

Other business donors to Good Beginnings Alliance’s Children’s Action Network include First InsuranceCo. ($15,000), Hawaiian Electric Industries ($10,000), Bank of Hawaii ($5,000) and the Hawaii Carpenters Market Recovery Program, also known as the Pacific Resource Partnership ($5,000).

The proposed amendment has pitted some early learning advocates against the Hawaii State Teachers Association, which represents about 12,500 public school teachers.

Hawaii is one of 10 states without state-funded universal preschool. Efforts to create a mixed-delivery preschool system have been stymied because 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 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.

The Good Beginnings Alliance has argued that a mixed-delivery system is the quickest and most cost-effective route to expand capacity and serve more keiki. About half of the state’s 3- and 4-year-olds enter kindergarten without a preschool education.

But the teachers union opposes the idea, arguing instead that a public preschool program should be built within the public school system to serve all children, free of charge. The union contends that subsidizing tuition at private preschools will take money away from public schools.

A group of retired HSTA officers formed a ballot issue committee — For the Future of Our Keiki — to lobby against the proposed amendment. (The committee’s officers include Roger Takabayashi, former HSTA president and vice president; Georgiana Alvaro, a past chief negotiator for the union; and Susan Bitler, a former deputy executive director and governance specialist for HSTA.)

The committee has reported a single contribution: $275,000 from the National Education Association. HSTAis the state affiliate of the National Education Association, which contends that public schools should be the primary provider of pre-kindergarten programs.

For the Future of Our Keiki spent a little more than $134,300 between Aug. 10 and Oct. 20, mostly on TV and radio ads against the proposed amendment. It also paid Honolulu-based Fuel Communications about $20,000 for consulting services and to coordinate media buys.

Since late September the group has bought more than 200 TV ads: 85 spots on the major TV networks and nearly 150 spots on stations that air multicultural programming, according to an analysis of advertising contracts filed with the Federal Communications Commission.

The Good Beginnings Alliance, meanwhile, reported spending $500,012 between Aug. 10 and Oct. 20 on "media television" with Virginia-based firm Screen Strategies Media.

Contracts on file with the FCC show the group has purchased more than 500 advertising spots on the major networks since late September.

The group also paid the Washington, D.C.-based Hamburger Co. $38,100 for a social media campaign and television shoot, and about $6,900 to local public relations firm Hastings and Pleadwell.

Amid the competing advertising, support for the amendment has been declining in recent months.

AHawaii Poll taken this month found 50 percent of voters would support the preschool amendment, while 42 percent said they would vote against it.

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.