California voters would decide whether to fund a major expansion of housing and treatment for residents suffering from mental illness and addiction, under the latest proposal by Gov. Gavin Newsom to address the state’s homelessness crisis.

Newsom announced Sunday that he will ask allies in the Democratic-controlled Legislature for a measure on the 2024 ballot to authorize funding to build residential facilities where up to 12,000 people a year could live and be treated. The plan is the latest by the governor who took office in 2019 vowing to own the issue of homelessness in a state where an estimated 171,000 were unhoused last year.

The governor called the plan the next step in how California expands services for unhoused people, especially those with psychological and substance use disorders.

“We have to address and come to grips with the reality of mental health in this state and our nation. The question is, what can we do more and do better?” Newsom said at a news conference.

California, home to nearly 40 million people, has nearly one-third of the nation’s homeless population, and their numbers are growing much faster than in other states, according to an analysis of federal data by the Public Policy Institute of California. Tent encampments have popped up on sidewalks and under freeway overpasses, and people in clear mental health crisis are a common sight on city streets.

The initiative would be partially funded by general obligation bonds that would raise between $3 billion and $5 billion to go toward construction of “campus-style” facilities along with smaller homes and long-term residential settings, Newsom said.