Voters have passed a controversial San Francisco ballot measure requiring drug tests for most welfare recipients, a sign of a rightward political shift in the historically progressive city.

As of Wednesday, Proposition F, backed by Mayor London Breed, had about 63% support. The measure will require people receiving monthly payments from the city’s cash assistance program for the poor to undergo drug testing if they are “reasonably believed to be dependent on illegal drugs.”

If they then refuse to comply or accept treatment for drug use, they will be deemed ineligible for the benefits.

People with young children and or who are over 65 years old are exempt.

“We want people to seek treatment and many people do, but the reality is others are not willing or able to do so,” Breed, who’s up for reelection in November, said in a statement. “Prop F will help get people into care. We are also sending a message that we are a city that offers help but not a city where you can just come and do whatever you want on our streets.”

More than 5,700 San Franciscans currently receive benefits, which can be as much as $712 a month in a notoriously expensive city.

The city’s Human Services Agency will be tasked with implementing the drug testing policy in the coming months.

Prop F had strong opposition from health care providers, including from Health Right 360, a San Francisco-based drug treatment center that offers services in nearly a dozen California counties, and the San Francisco AIDS Foundation.

“I have seen addiction and overdose worsen when people lose support systems, and that is what Proposition F threatens to do,” Dr. Marlene Martin, director of the Addiction Care Team at the University of California, San Francisco, said at a press conference last month.

“Prop F only layers on punishment, shame and social isolation while stripping people of resources to survive,” Gary McCoy, vice president of policy and public affairs for Health Right 360, said at that same press conference.

The San Francisco Democratic Party also came out against the measure.

San Francisco is in the midst of a major drug epidemic, with synthetic opioids like fentanyl flooding the streets. Last year was the city’s deadliest year on record for drug overdoses, according to a tracker by The San Francisco Chronicle.

It wasn’t the only conservative-leaning measure San Francisco voters backed on Tuesday. Prop E ― a measure authorizing police use of drones and surveillance cameras, limiting reporting requirements for use-of-force incidents and expanding when police may pursue suspects in vehicles ― also passed. It too was backed by Breed.

Need help with substance use disorder or mental health issues? In the U.S., call 800-662-HELP (4357) for the SAMHSA National Helpline.