The largest affordable housing bond in California history is officially headed to the November ballot — just not for all Californians.

On Wednesday, commissioners of the Bay Area Housing Finance Authority — a first-of-its-kind regional agency with the ability to borrow and spend taxpayer dollars —  agreed to ask voters across the nine counties of the Bay Area to approve an IOU of up to $20 billion dollars. The bulk of the funds would go toward the construction of new subsidized housing projects, with the rest to be spent buying up existing units (to make or keep them affordable) and on housing-related infrastructure.

The historically huge bond is being sent to the ballot at a time when the future of a long-sought statewide housing bond looks uncertain at best.

A lot will ride on the outcome of this bond vote — both economically and politically.

Affordable housing developers lined up in support at Wednesday’s hearing, noting that thousands of housing units reserved for working class Bay Areans are ready to break ground but lack the public funding to do so.

“We have entitled projects now that cannot get financed through the system,” said Nevada Merriman, vice president at MidPen Housing, a nonprofit developer. “There’s a pipeline here. It’s ready to go.”

The Bay Area authority says the funds could be used to build and acquire up to 72,000 units. That housing would range from the most deeply affordable — homes reserved for people on the brink of homelessness — to “moderate” income households. In San Francisco, San Mateo and Santa Clara counties, that includes those making more than $150,000.

California housing regulators have tasked local governments across the Bay Area to plan for roughly 250,000 affordable units by the end of the decade.

The bond is also a test case of a new approach to funding affordable housing in California. State lawmakers gave regional planners across the Bay Area the greenlight to set up the finance authority in 2019. If this first bond passes, most of the proceeds will go out in the form of low-cost loans.

“We’re very intent on setting up a successful public interest mortgage lending system so that we are self-sustaining,” said Kate Hartley, the authority’s director. “Our goal is to get good quality housing out as quickly as possible and to meet that need — and to the people who fear that we won’t do a good job, to really prove them wrong.”

But big borrowing comes with a big cost. The authority estimates that paying off principal and interest will add up to nearly $50 billion, to be paid via higher property taxes — a couple hundred dollars per year for the average Bay Area homeowner.

Even for one of California’s most reliably progressive regions, that’s no sure thing. Last March, a mental health housing and treatment bond was backed by Gov. Gavin Newsom and supporters spent nearly 15,000 times more than the opponents. Still, Prop. 1 passed by less than half of a percentage point.

Recent polling commissioned by the Bay Area Housing Finance Authority, the results of which were detailed at the hearing, found that 54% of likely voters support the bond. That may be more than a majority, but in California, where most local bonds require the backing of two-thirds of voters, that isn’t enough to pass.

That could change this November. Legislators are putting the finishing touches on a constitutional amendment to slash the threshold needed to approve local housing and infrastructure borrowing to 55%. That change is headed for the November ballot — and if it passes, it would apply to any bond concurrently on the ballot. That includes the Bay Area bond.

That means the fate of California’s largest-ever housing bond may hinge on the outcome of not one ballot measure, but two.

If they fail, affordable housers may not be able to turn to the state for backup.

Last year, Oakland Assemblymember Buffy Wicks introduced a $10 billion affordable housing bond, partly to replenish the coffers of the state’s premier affordable housing program, which was funded by a prior bond in 2018. As now, housing costs and homelessness were a top concern for voters. With state funding running low, the odds that legislators would sign off on Wicks’ proposal and send it to the voters later this year looked good.

But the political winds have shifted.

Affordable housers did relatively well in this austere budget cycle. That has given advocates less political juice as Legislative leaders consider competing priorities to fund with borrowed cash — namely, school buildings and climate programs.

Lawmakers have until July 3 to decide which bonds will make it onto the November ballot and which will be shelved.

Ben Christopher is a reporter with CalMatters.