Total and complete victory. For a niche technocratic movement hyper-obsessed with increasing the supply of housing, that’s what the past few weeks in Democratic politics have felt like. In recent years, a remote-work-induced housing-market boom has pushed housing affordability higher on the national political agenda. And years of advocacy by yes-in-my-backyard, or YIMBY, activists has familiarized politicians with the logic of the housing shortage.

Vice President Kamala Harris knows “that if we want to make it easier for more young people to buy a home, we need to build more units and clear away some of the outdated laws and regulations that made it harder to build homes for working people in this country,” as former President Barack Obama proclaimed on the second night of the Democratic National Convention last month.

In her acceptance speech two nights later, Harris declared to raucous cheers, “We will end America’s housing shortage.” Her campaign has since focused even more intensely on the issue, launching a “housing blitz in the battlegrounds,” complete with a dedicated ad.

That senior members of the Democratic Party believe America’s housing shortage is driving the affordability crisis should not be surprising. Over the past two decades, the need for more homes is the closest thing to a consensus that technocrats and experts have. Across a range of ideological sources, academic studies, think-tank reports, real-estate-industry analyses, and state-level legislation have all come to the conclusion that rising home prices and rents are the result of a dwindling supply of houses.  What is surprising is the willingness of national Democratic politicians to foreground this issue—on which state- and local-level Democratic politicians are severely divided.

Last week, pro-housing advocates hosted a “YIMBYs for Harris” fundraising video call on which prominent elected officials such as Colorado Governor Jared Polis, Maryland Governor Wes Moore, San Francisco Mayor London Breed, and Senator Brian Schatz of Hawaii spoke in favor of Harris’s focus on the housing crisis.

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But for a movement used to operating in local town halls and making bipartisan deals in statehouses, this newfound attention can be disconcerting. Alexander Berger, the CEO of Open Philanthropy, an early and current funder of the pro-housing movement, told me that he’s generally pleased by national Democrats’ convergence on the issue but raised one “note of caution”: the possibility that “the most famous Democrats highlighting this issue … make it a more polarized issue.” In other words, if YIMBYism becomes identified with Harris and other elite Democrats, will Republican state legislators be more likely to oppose pro-housing bills?

As I reported earlier this year, some prominent movement advocates were relieved when President Joe Biden’s State of the Union didn’t take a strong stand on housing politics. Similarly, while many pro-housing advocates celebrated on X and other social-media platforms during the convention, others worried behind the scenes about a backlash.

Housing-development regulations generally rest with state and local governments. Although the U.S. government can help with financing, particularly of affordable housing, and can use federal dollars to nudge states to adopt better policies, most experts believe that plausible federal interventions on increasing the housing production are likely to have marginal effects; stronger measures seem politically impossible.

Those afraid of elite Democrats polarizing this issue are misreading the political economy of the housing shortage. The affordability crisis is being driven by Democrat-led states and cities. If downballot Democrats get on board with Harris and Obama, then elected officials in charge of housing policy in highly restrictive California, New York, and Massachusetts will face immense pressure to change course. This will have downstream benefits for the whole country. As people are pushed out of expensive cities such as San Francisco and Boston, they move to more affordable markets, creating upward pressure on prices there. But moving to your second-choice housing market has a major drawback: When people are priced out of living near the jobs that are the best match for them, that hampers the entire economy; productivity, GDP growth, and wages all suffer.

I also doubt that greater polarization by Republicans against housing reform will have much real-world impact in any case. As president, Donald Trump tried pushing the message that Democrats were out to “destroy the suburbs,” after Senator Cory Booker of New Jersey proposed to provide grant funding to jurisdictions that updated their own zoning to ease the construction of affordable homes. And yet one of the biggest pro-housing success stories has been pro-Trump Montana Governor Greg Gianforte’s slate of reforms—the “Montana Miracle”—that passed last year.

Yes, some helpful bills might fail in the short term, particularly in Republican-led statehouses. But the pro-housing movement’s biggest recent defeat came at the hands not of a Republican, but of Arizona Governor Katie Hobbs, a Democrat who vetoed an ambitious bipartisan starter-home bill, prompting backlash from progressives and conservatives alike. Republicans’ commitments to business and economic growth can lead them down a pro-housing policy path. Even if Trump or Harris polarizes national Republicans against equity-minded zoning reform, booming red states such as Texas and Florida are unlikely to turn resolutely against development and growth, the twin staples of their political success.

As Trump once famously suggested, people can become tired of too much winning. Movements used to operating in the shadows often stumble when they meet their moment. Strategies optimized for persuading legislators in meetings may falter under the scrutiny of a national electoral campaign. The most common problem is that winning the battle of ideas online or in the ivory tower does not necessarily translate into progress on outcomes.

In general, Democrats are comfortable in the world of demand-side policies—which is to say, in providing subsidies so people can afford existing goods or services—but the housing crisis is fundamentally a supply-side problem. By tying housing unaffordability to the housing shortage, Harris is countering arguments that many downballot Democrats find persuasive: that there is no shortage, that new construction isn’t the answer, that redistributing existing housing would be sufficient.

Harris isn’t turning away from demand-side strategy. One of her most touted housing policies is $25,000 in down-payment assistance for all eligible first-time homebuyers (eligibility criteria have not yet been detailed). Programs like this are popular and sound promising at first blush, but a large expansion of demand-side programs in a supply-constrained market leads to higher prices. One study of low-income housing markets found that landlords were able to charge higher rents when housing vouchers were made more generous. Another study found faster rent growth in areas with a larger demand subsidy. In order to prevent the down-payment assistance from being absorbed by property owners through higher home prices, the demand subsidy would need to kick in after a lot of new housing stock has been built—an issue that a senior campaign adviser, who requested anonymity to freely discuss internal policy deliberations, told me the campaign well understood.

Regardless, the biggest obstacle facing the pro-housing movement is that many of the legislative victories have yet to translate into significantly more homes being built. Housing markets can take a long while to adjust to legal changes; many major reforms were passed in just the past couple of years. But reorienting local governments toward building rather than slowing down development takes more than time; it also takes continued political effort. In 1982, a statewide bill in California legalized accessory dwelling units (ADUs)—small secondary units, also known as casitas, mother-in-law suites, or garage apartments, that homeowners build on their property.

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But the law also allowed intransigent local governments to set standards that made building ADUs prohibitively expensive. As a report by the pro-housing organization California YIMBY explains, “In practice, most local jurisdictions adopted onerous and unworkable standards that resulted in few ADUs being permitted for 34 years.” Some cities dominated by homes on 5,000-square-foot lots allowed ADUs only on lots larger than 7,500 square feet, a researcher found.”

Lawmakers tried to enact more reforms, to little effect. Finally, in 2016 and 2017, a suite of new laws went much further to push cities to allow more ADUs. The state had finally prevailed, and from 2017 to 2021, 68,000 new ADUs were constructed. And by 2022, nearly one in five homes produced in California was an ADU.

This sort of fine-tuning is necessary to figure out what the exact roadblocks to construction are. But what would be even better is if cities themselves felt motivated to be partners in producing more housing rather than obstacles. That’s what makes the national Democrats’ sweeping new tone on housing policy so exciting. Trying to get housing advocates to hold every blue-state local government to the letter of the law is time-consuming and expensive. Convincing them that their partisan and ideological commitments require figuring out how to build more housing would be much more effective.