Last fall, Krista Greene missed a week of work after her sons were exposed to Covid and could not return to school. Greene, who manages a tutoring center and yoga studio in Charleston, West Virginia, does not receive any paid time off. Normally, she would have been worried about this loss of income. But the Greene family’s budget had recently become a little more flexible, thanks to the monthly child tax credit payments that began in July 2021.

“The first thing I said to my husband was, ‘The Biden bucks are coming next week, so I won’t miss any bills,’” Greene said.

It was nice while it lasted.

Families probably received their final monthly payments in December after Congress failed to pass the Build Back Better Act. The legislation, the cornerstone of the Biden administration’s domestic policy, would have made the payments permanent. But one Democrat stood in the way – Greene’s senator, Joe Manchin.

A week before Christmas, Manchin appeared on Fox & Friends and announced he would not vote for the Build Back Better Act, effectively poleaxing Biden’s plans in a Senate evenly divided between Democrats and Republicans.

“I have always said, ‘If I can’t go back home and explain it, I can’t vote for it,’” Manchin said in a press release after the television appearance. “Despite my best efforts, I cannot explain the sweeping Build Back Better Act in West Virginia and I cannot vote to move forward on this mammoth piece of legislation.”

The announcement came after months of negotiations between Manchin and the White House, some of which involved the child tax credit. Manchin wanted to limit the credit to families making $60,000 or less annually. He has also said he will not support a permanent credit unless it includes a work requirement.

The child tax credit was one of a number of Biden proposals that were surprisingly popular in the deeply Republican state of West Virginia – not least because Manchin’s constituents have benefited from it more than most.

Ninety-three per cent of West Virginia children – about 346,000 in all – qualified for the credit payments. That extra $250 to $300 per child a month lifted about 50,000 of those children above the poverty line, according to the West Virginia Center for Budget and Policy (WVCBP).

Now that the credits have vanished, so will those advancements. The timing could not be worse. Like the rest of the country, West Virginia is suffering a surge in inflation unseen in decades, a surge that disproportionately affects the poor.

“The checks aren’t coming on,” said the WVCBP executive director, Kelly Allen. “Fifty thousand kids in West Virginia are at risk are dropping into deep poverty.”

Queentia Ellis is a single mother with three daughters, ages seven, three and two. For a while, she supported her family with a minimum wage job but found she was always coming up short. “It’s impossible to take care of three kids on a minimum wage job,” Ellis said.

She decided to get a college education. The monthly child tax credit payments, along with child support and Temporary Assistance for Needy Families (TANF), allowed her to stay home with her kids while taking classes full-time.

“It helped me pay my bills and buy things for my kids that they needed,” said Ellis, who hopes to someday start her own business.

With the monthly payments ended, Ellis said she will probably have to return to a minimum-wage job, which means it will take longer to complete her college degree. She will also have to find childcare for her daughters, which will cost up to $100 a month for each child, even with help from a state childcare assistance program.

“That takes a toll on the income, especially if you’re working an hourly minimum wage job,” Ellis said. “I have to figure out what and how I’m going to go about making things possible. But where there’s a will there’s a way.”

After announcing he would not support the Build Back Better Act, reports surfaced that Manchin was concerned parents were using the child tax credit to buy drugs.

But the evidence shows that in West Virginia and across the country the money was spent on necessities – 91% of low-income families used the money for basic needs like rent, groceries, school supplies and medicine, according to the Center on Budget and Policy Priorities’ analysis of US census data.

“Families know what they need. In some cases, that’s putting food on the tables. In some cases, that’s paying rent. In some cases, it’s allowing mom to stay home for a few months, or paying for childcare because mom needs to go to work,” Allen of the West Virginia Center for Budget and Policy said.

Hunter Starks is a single parent with a four-year-old daughter. Theypreviously worked as a social worker, while also working part-time as a political organizer, often logging more than 50 hours in a week.

But things changed in 2021.

“I’ve worked since I was 15, usually multiple jobs. And I’ve never had a hard time finding work like I did this year,” they said.

Starks had difficulty finding employment because they could only take jobs with hours that aligned with their child’s daycare hours.

“Service jobs and fast food don’t need folks during those hours,” they said.

Starks said the $300 child tax credit payments were “the difference between getting by or not”.

“And I still had to ask multiple folks for help,” Starks said.

Starks said January’s budget will be tight without the tax credit payment, “but it’s been tight”.

They will soon start a new full-time job as a paralegal, in addition to their part-time organizing work. While that will help their bank account, Starks said it will mean less time with their daughter.

“I kind of hate the fact that I’m going to go back to working multiple jobs and spending less time with my daughter,” they said. “Even though I’ve struggled financially, I’ve appreciated having that time with her.”

While Manchin has balked at the child tax credit’s price tag – about $100bn a year – the credits pumped $470m into West Virginia between July and December 2021 alone. Allen said that money was probably immediately reinvested in the state’s economy, since low- and middle-income families typically spend tax refunds as soon as they receive them.

Yoga studio manager Krista Greene said that’s why it was so important the payments arrived monthly instead of once a year, at tax time.

“It became part of your monthly income,” she said. “If a hospital bill comes around, I can’t say, ‘Can you wait four or five months until I get my income tax?’”

Allen also said the money would have long-term positive effects on the state’s economy as well. Living in poverty has a deleterious impact on children’s health, education and future earnings.

“If kids are lifted out of poverty and have access to more economic security, it pays for itself in the long term,” Allen said.

Manchin’s office declined the Guardian’s request for comment.