People who study child poverty call the expanded child tax credits enacted in March a rousing success. A study released Wednesday by Columbia University’s Center on Poverty and Social Policy found that November’s payments of up to $300 per child kept 3.8 million kids out of poverty, following five months of the program keeping 3 million to 3.6 million children above the poverty line. 

The sixth round of checks, which went out Wednesday, was the last, unless Democrats renew the program in their Build Back Better bill.

Studies suggest the direct payments to parents, who can then decide how best to spend the money for their families, will cut child poverty by 40 percent, benefiting 9 of 10 U.S. children, The Associated Press reports. Stopping the CTC payments would be “a real slap in the face for families in need,” says Children’s Defense Fund poverty policy director Emma Mehrabi. “There is no other tool in our toolkit that has significantly reduced child poverty for decades.”

The final remaining hurdle to passing Build Back Better appears to be Sen. Joe Manchin (D-W.Va.). Manchin said Wednesday that reports he wants to strip the child tax credit from the legislation are “a lot of bad rumors,” and he’s “always been for child tax credits.” When reporters asked if that included the revamped program that sends checks to parents, he said, “I’m not negotiating with any of you” and called such questions “bulls–t.”

Manchin’s colleagues appear to think he’s not keen on the expanded CTC. Sen. Michael Bennet (D-Colo.) said based on their “many, many, many conversations,” Manchin “is not at this moment a fan of the Child Tax Credit,” though he has hopes. The Build Back Better bill extends the program for just one year, to keep down its price tag.

At a Wall Street Journal event last week, Manchin said the bill’s “social” spending may feed inflation and suggested the one-year extension is kind of gimmicky. “If we keep sending checks,” he said, “it’s going to be hard to stop the checks.”

Manchin isn’t the only thing keeping the Jan. 15 checks from going to families. Sen. John Thune (R-S.D.) said Tuesday that Republicans are fine letting the $300-per-child CTC payments lapse. “The thing I don’t think you want is a huge spike in spending,” he told reporters. “And that would probably be the most obvious example of an inflationary type policy.”