A $46 billion federal program enacted by Congress to prevent evictions during the pandemic got off to a sluggish start last year, but is now distributing cash so quickly that many states are running out of money, endangering millions of struggling tenants who depend on the support.

On Friday, the Biden administration announced that 665,000 households had received aid through the Emergency Rental Assistance Program in November, the most ever for any month, bringing the total distributed or slated to be spent to between $25 billion and $30 billion, according to the Treasury Department.

But that success means that several states, including New York, Texas and Oregon, have already used up nearly their entire share of federal funding from the program.

And the new numbers underscore the reality that the federal government’s largest-ever attempt to prevent evictions was never intended to be a long-term solution. Funds for struggling renters will soon disappear unless Congress renews funding, which is highly unlikely.

“There is tremendous uncertainty now, especially for renters,” said Vincent Reina, a professor of urban planning at the University of Pennsylvania who has helped design aid programs in Philadelphia. “Historically, we have had a nonexistent housing safety net nationally. Then we suddenly have this allocation of resources, and we build this whole new infrastructure. Now it’s about to go away, and we have no idea if it will ever be rebuilt.”

Those who have already received rental assistance can keep it. But renters who want to file for the first time or reapply may be out of luck.

Many states had expected to see a major windfall this month, as the Treasury Department shifted $1.1 billion from states that had been slow in distributing funds.

Instead, the White House pressed Georgia, Arizona, Wisconsin, Louisiana and other states to voluntarily shift about $875 million to cities and counties in their states that needed the money most. As a result, only a relatively small amount of funding was available to states who requested more.

New York, for example requested a billion dollars in added funding but stands to receive only $27 million, or 3 percent of what it asked for.

John Mitchell used rental assistance to remain in his Philadelphia apartment when he fell behind on rent, after losing his job as a restaurant server because of pandemic closures.

But now, with the surge of the Omicron variant, he is back in the same position. The restaurant where he works closed after a staff member tested positive for the coronavirus. Mr. Mitchell got sick, too, and now he is behind on rent again while he looks for a new job and cares for his mother, who is struggling with health issues.

“This has just been hell,” he said.

Landlords are facing uncertainty, too.

“This program is a lifeline — it’s how we right the ship, if we will, on housing during the pandemic,” said Greg Brown, senior vice president of governmental affairs at the National Apartment Association. Owners who can’t receive additional rental assistance will be left with mounting debts, he said. “There clearly is more need than there were dollars allocated.”

For months, emergency rental assistance dollars sat largely unspent, with states and cities struggling to set up programs to distribute the funds, and tenants and landlords bogged down with cumbersome application requirements. Through July, just $5.1 billion of the $46.5 billion had been distributed.

But as the White House and the Treasury Department, which oversees the program, put pressure on states to spend the funds or else see them used by other states, the pace sharply quickened.

One of the major levers the government used was to warn laggard states that their funding would be shifted to other states if they did not quickly improve their distribution and anti-eviction efforts.

By the fall, when the federal evictions moratorium expired, many states improved their efforts, and administration officials began offering governors an out: They could move their money to counties and cities that were spending the cash more efficiently, said Gene Sperling, an economic adviser to President Biden who oversees the program for the White House.

Arizona officials agreed to shift $39 million to the state’s largest county, Maricopa, while Georgia moved about $50 million from its allocation to Fulton and DeKalb Counties in the Atlanta area. The biggest single shift took place in Wisconsin, where Gov. Tony Evers, a Democrat, agreed to move about $110 million to county and city officials in Milwaukee, according to the Treasury Department.

That left only about $240 million in cash to be shifted from states — including Vermont, Idaho, Delaware and South Dakota — that were not spending their cash fast enough.

“That is disappointing to states and cities who hoped to have a large amount of additional funds reallocated to them, but it reflects the larger, positive reality that after the initial challenges, these funds are now being spent or committed to families in need at a much more accelerated pace,” Mr. Sperling said.

For example, Texas requested $3 billion from the Treasury in the reallocation process, according to Michael Lyttle, a spokesman for the Department of Housing and Community Affairs. The state will not receive additional funds, but several Texas cities and counties will receive around $19 million total.

“This is the only life vest,” said Dana Karni, manager of the Eviction Right to Counsel Project in Houston. “If we don’t have emergency rental assistance, there’s not a whole lot we can do.”

The city of Houston and Harris County have just under $10 million left in their local emergency rental assistance coffers after distributing more than $170 million. The state stopped accepting new applications in November, after requests exceeded available funds.

For months, the assistance funds helped keep people housed, even as local eviction filings have climbed back up toward prepandemic averages, Ms. Karni said.

The rental assistance funds, in combination with local eviction protections in some places, have been effective at preventing a surge of evictions that many feared would come on the heels of the end of the federal eviction moratorium in August.

The number of new filings nationally remains below prepandemic levels, according to Princeton’s Eviction Lab, which collects data from housing courts around the country.

But tenants fear that the loss of the aid, and the lapsing of local anti-eviction protections implemented during the pandemic, will eventually lead to a rise in evictions.

For Robin Millard, rental assistance was the difference between staying in her home and possible homelessness. After her roommate lost construction work because of Covid, the two fell behind on rent for the Houston apartment Ms. Millard also shares with her 11-year-old daughter. Ms. Millard had costly medical bills to pay for her own cancer treatment, too, and her disability checks were not enough to cover it all.

The assistance changed her life, she said.

“I know that I definitely would have been homeless with my daughter, which is a terrifying thought because we’ve never been unstable in our lives,” Ms. Millard said.

“It’s scary to think that that isn’t going to be available anymore, because where else are people going to turn to?” she said.

Landlords and tenants in some places continue to be frustrated by monthslong wait times to actually receive the funds.

“Rental assistance has just been a botched mess in Philadelphia from our side of things,” said Kevin Moyer, a property manager in the city. He said that delays in rental assistance funds had led his clients to move forward with evicting tenants rather than wait for payments.

“People are still being evicted,” said Myriam Ramirez, an organizer in Philadelphia with Make the Road PA. Some tenants have struggled with filling out the complicated application, and others have faced delays because their landlords failed to complete their portion. “They call me every day: ‘What do we do? Who do we call?’” Ms. Ramirez said.

The sudden exhaustion of rental assistance funds also casts uncertainty on the future of new eviction prevention programs that dozens of city and states used rental assistance money to fund.

Some jurisdictions established eviction diversion programs to provide mediation during landlord-tenant disputes. Others created programs that provided tenants with legal representation in eviction proceedings.

But without rental assistance funds, the effectiveness of these programs is limited.

In Texas, courts will be required to allow legal representation for tenants at least until March thanks to an order from the Texas Supreme Court. But without financial relief for renters, Ms. Karni said, lawyers have limited impact. “If we don’t have emergency rental assistance, there’s not a whole lot we can do,” she said.