The Small Area Fair Market Rent program was not without detractors, even among Democrats. New York lawmakers, including Representative Nydia Velasquez, a Democrat, and Senator Chuck Schumer, also a Democrat, protested that the policy would require more renters to either move or pay more money out of pocket, because their vouchers would be worth less money if they stayed in high-poverty neighborhoods. Rick Gentry, the chief executive officer of the San Diego Housing Commission, which administers the Section 8 program for San Diego, one of the 23 metropolitan areas that would have had to adopt the new Small Area Fair Market Rents for the region, told me that “the way HUD rolled it out was bureaucracy at its worst” and that the program amounted to “mandated social engineering.” San Diego would have had to manage payment standards in 23 different zip codes, he said, which would have been administratively challenging. Gentry estimated that the program, if administered, would have required 6,500 of his households to pay more in rent or to move, because they lived in areas where their vouchers would have been worth less. San Diego voucher holders should have the choice of being able to move to different neighborhoods, he argued, but not be forced to do so by changing program standards.

Many public-housing authorities were also concerned that the rule would destabilize low-income neighborhoods by encouraging tenants to move out, and by setting payments lower for apartments there. Most housing authorities support the idea of helping people move to high-opportunity areas, but they have not yet found the best way of doing that, Sunia Zaterman, the executive director of the Council of Large Public Housing Authorities, told me. “A one-size-fits-all approach rarely works,” she said.

And yet, this wasn’t a program that was rushed to implementation or that materialized out of bureaucrats’ brains with no testing or little process. HUD had tried out the program in five housing authorities beginning in 2012. A report about that trial found that the program had big benefits. One of the positives: The share of households moving to high-rent zip codes in the test areas increased from 18 percent in 2010 to 28 percent in 2015. Under the program, “the availability of units is much more evenly distributed across different types of neighborhoods, leading to increased availability in high-rent zip codes,” the report found. At the same time, there were also drawbacks. Though more apartments became available in high-rent zip codes, fewer were available in low-rent zip codes. Across all the markets tested, there were 3.4 percent fewer units available overall.

Still, some public housing authorities cheered the program. One of the demonstration areas, the Housing Authority of Cook County, in Illinois, told me that it wanted to continue using Small Area Fair Market Rents because without them, “we would not be able to move people into higher opportunity areas.” And David Nisivoccia, the president and CEO of the San Antonio Housing Authority, said his agency was all ready to begin using Small Area Fair Market Rents. The housing authority got notice in late 2016 that it would be required to use the new standard, and its staff had prepared accordingly. “Ultimately, any time you give a client more choice about where they can live, that’s a good thing,” he told me.