Infrastructure Bill Would Add $256 Billion to Deficit, Analysis Finds

The Committee for a Responsible Federal Budget, a nonpartisan fiscal watchdog group, has also taken issue with the lawmakers’ accounting. For instance, senators estimated $200 billion in savings from unused funds from earlier pandemic relief packages. But the committee said those savings had already occurred, so they should not count as an offset for the cost of the infrastructure bill, which it estimated would have a net cost of about $350 billion.

Marc Goldwein, senior policy director at the committee, said that the Congressional Budget Office’s deficit projections were not capturing the additional spending that Congress would be authorizing in the bill and that the offsets did not appear to raise as much revenue as lawmakers anticipated. He estimated that the bill could actually add more than $400 billion to the national debt.

“It’s a bit worse than I thought,” Mr. Goldwein said.

Figuring out how to finance the legislation had been one of the thorniest aspects of negotiating the bill, after Republicans ruled out raising taxes and beefing up I.R.S. enforcement of tax cheats and Democrats balked at increasing fees for drivers. Republicans have been expressing growing concerns about the cost of the Biden administration’s economic agenda, arguing that the flood of spending would cause inflation and inflict grave economic damage.

At least one moderate Democrat, Senator Joe Manchin III of West Virginia, has said he has concerns about inflation; on Thursday, Mr. Manchin wrote a letter to Jerome H. Powell, the Federal Reserve chair, declaring, “It’s time to ensure we don’t overprescribe the patient by further stimulating an already strong recovery and therefore risk our ability to respond to future crises.”

Republicans have also declared that they will not support a move to raise the debt ceiling, which the Treasury Department says technically was reached at the beginning of this month. The department is taking what it calls “extraordinary measures” to avoid breaching it, but that is projected to happen in October without action by Congress to raise it.

Some Republicans have hammered the infrastructure legislation for its budgetary gimmicks, arguing that they far outweigh the merits of the spending.

“If we weren’t going to provide real ‘pay-fors,’ then we should have just seen from them an admission from the outset: ‘We’re not going to pay for it,’ ” said Senator Mike Lee, Republican of Utah, at a news conference on Wednesday. “Instead, they said it’s going to be paid for, and then they release it and say it is paid for — only there are some asterisks next to that.”