Supporters say public funding is needed because families often cannot afford the full cost of care, while providers struggle to cover expenses and pay educators enough to keep them in the field. A county advisory council appointed by supervisors would assess local needs and recommend how the money should be spent, with the ability to shift priorities as conditions change.

The proposal comes amid a statewide shortage: nearly 2 million California children qualify for state-subsidized child care, but available funding is not enough to serve them all, according to the California Budget and Policy Center. Marin has faced similar gaps before. A child-care funding measure there failed in 2016, falling three percentage points short of the two-thirds support then required.

Other Bay Area counties have used local taxes to support care. San Francisco directs revenue from a commercial-building tax toward child-care costs for low-income families, while Alameda County has used sales-tax revenue to raise early-childhood educators’ wages. Those efforts reflect a broader challenge in the sector: low pay can drive turnover, while increasing wages without additional funding can make care even less affordable for families.

Child-care shortages also affect employers, said Paula Reynolds, director of strategic projects for the Mill Valley Chamber of Commerce. Businesses rely on workers being able to show up consistently, she said, and dependable child care helps employers plan their operations.

The Coalition of Sensible Taxpayers is urging voters to reject Measure P. The group says employers, rather than taxpayers, should contribute to child-care funding and argues that residents are already under pressure from inflation and a wave of proposed taxes, bonds and fees. The coalition has also criticized the measure for not specifying exactly how its revenue would be allocated. Board member Lucy Dilworth declined an interview request.

Supporters say the flexible spending structure would let the county respond to changing needs, including the possibility of directing more money toward the child-care workforce or expanding facilities. Joanne Webster, president of the North Bay Leadership Council, which backs the measure, said new taxes should be scrutinized but voters should also weigh the consequences of leaving the problem unaddressed.

The timing could matter for future local tax campaigns. Proposition 43, also on the November ballot, would require future citizen-led ballot initiatives to win two-thirds support to pass. Marin’s 2016 child-care measure narrowly missed that threshold. Court decisions since then have made it easier to pass similar citizen-led tax measures, supporters say, but they warn that could change if Proposition 43 is approved.