The child tax credit payment, the first of its kind, began in July of this year. Americans have been using the extra money—up to $300 per child per month—to help pay their rent, child care costs, and feed their families. The payments have been wildly successful. They reached about 61.1 million children in October, contributing to a 28% decrease in child poverty compared to the rate it would have been without the credit, according to researchers at Columbia University. 

But that all is set to be disrupted or even end permanently, because it’s unlikely the Senate will be able to pass the estimated $2 trillion Build Back Better Act—which the child tax credit is attached to—before the end of the year. Currently, the sweeping social legislation is set to extend the credit, which provides up to $3,600 for children under the age of 6 and $3,000 for those 6 through 17, for another year. The House passed a version of the package last month, putting the ball now in the Senate’s court. 

“It would be a tragedy if, because of our dysfunction, we find ourselves in a place where we’re doubling childhood poverty,” Sen. Michael Bennet (D-Colo.) told Fortune. Bennet has worked for years to boost child tax credit rates from their previous annual level of $2,000 per child. The 2021 expanded child tax credit, which passed as part of the American Rescue Plan earlier this year, is based on the American Family Act, legislation that was introduced (but never passed) by Bennet and Sen. Sherrod Brown (D-Ohio) in 2017. 

“What the child tax credit proved was that we don’t have to accept [childhood poverty] as a permanent feature of our democracy or of our economy. If we are going to go right back to where we were before we did that, shame on us,” Bennet says. 

If Congress doesn’t extend the expanded child tax credit, an estimated 9.9 million U.S. children are at risk of slipping below the poverty line or deeper into poverty, according to an analysis by the left-leaning think tank, the Center on Budget and Policy Priorities. 

“It’s made a huge difference in terms of our poverty rate. We’ve cut child poverty in this country by a quarter this year,” Bennet says. “If we’re gonna stop the policies that achieve that, we’re going to see a vast number of kids going hungry.”

Despite the closing window to pass Build Back Better, Bennet is still optimistic it will happen before January. The provision already passed the House and has wide support among Democrats. “I believe the odds are high that we’re going to pass it by the end of the year and one of the reasons that we really have to get done is that the expanded child tax credit is one of the most significant policy changes for kids and families to come out of Washington in generations.”

But Bennet acknowledges there’s currently no backup plan if the Senate fails to act, and passing the legislation is going to be a struggle. Because Democrats have such a slim majority in the Senate, every vote counts and the party has yet to secure the 50 votes needed to pass the Build Back Better using the budget reconciliation process. Sens. Joe Manchin (D-W.V.) and Kyrsten Sinema (D-Az.) are still holding out.

Manchin, in particular, has publicly questioned the value of the child tax credit and the total cost of the Build Back Better agenda. “Whatever Congress is considering, we should do it within the limits of what we can afford,” he told CNN this week. Manchin has also raised concerns that the package would add to the already rising annual inflation rates, which ticked up to 6.8% in November. 

The U.S. Treasury disagrees, with Secretary Yellen saying the effect of the legislation on inflation is minimal. 

“As Secretary Yellen has said, the Build Back Better Act, which includes the advanceable Child Tax Credit, will lower costs for families and meaningfully reduce childhood poverty. As the Act is fully paid for over ten years, and makes long-term investments, it is not expected to add to inflation pressures,” a Treasury spokesman told Fortune.

Other experts also believe that the effect of this legislative package on inflation is negligible. 

“The Build Back Better legislation—including the Child Tax Credit provision—is unlikely to have a noticeable effect on the Federal Reserve’s ability to manage inflation,” says Chad Stone, an economist with the Center on Budget and Policy Priorities. “The monthly payments from the expanded Child Tax Credit are helping families cover rising costs and afford essentials like diapers, school clothes, and groceries. Congress should extend the CTC expansion to prevent millions of families from having the rug yanked out from under them, making it much harder for them to make ends meet.”

Bennet says it’s “very hard to tell day to day” if ongoing conversations with Manchin are helping to persuade the Senator of the merits of extending the child tax credit. 

“I know [Manchin] hates the child tax credit. I mean, that’s not a secret to anybody,” Bennet tells Fortune.

Some lawmakers have already speculated that they could pass the Build Back Better Act in January and make the child tax credit provisions retroactive. But Politico reports that IRS staff have told Democrats they need to pass the extension before Dec. 28 for the payments to continue going to families without an interruption.

This could mean that many American families will struggle come January, especially with holiday bills to pay and rising inflation pushing the price of basic goods higher. 

“It’s all hands on deck to try to get this done,” Bennet adds. “America’s kids don’t have much of a lobby in Washington D.C., especially America’s poorest. If they did, we wouldn’t have perpetuated this disgraceful amount of poverty that we have in our country for our kids.”