Senator Jeff Merkley (Ore.), the top Democrat on the Senate Budget Committee, claims a new analysis by the Congressional Budget Office (CBO) shows President Donald Trump’s One Big Beautiful Bill Act of 2025 (OBBB) “explodes the debt by trillions of dollars to fund tax breaks for billionaires.”

The OBBB was narrowly approved by the Senate and House earlier this year and includes provisions that make permanent the temporary tax rate cuts that became law in 2018. The measure also eliminates taxation of tips and overtime.

“Each and every analysis from the nonpartisan CBO continues to show the same result regardless of how you look at it: this bill explodes the debt by trillions of dollars to fund tax breaks for billionaires,” Merkley said in a statement.

“Republicans can’t spin the fact that this bill is bad policy that kicks more than 15 million people off of their health insurance, will force millions of kids to go hungry, and explodes the national debt by $5 trillion over the next 10 years — pushing the cost of this bill onto future generations to ensure billionaires can pay less in taxes. It is the height of hypocrisy coming from the party that claims to be fiscally responsible.”

The Oregon Democrat was referring to CBO’s response to his request earlier this year that the congressional economic forecasting agency assess the impact of the OBBB on the federal government’s debt and deficits. In its response to Merkley, CBO said it “estimates that the additional debt-service costs under the legislation as enacted will total $718 billion over the 10-year period. That change will increase the cumulative effect on the deficit to $4.1 trillion.”

The CBO estimates of the overall impact rises to $5 trillion when the calculation assumes the 10 key tax provisions of the OBBB will remain in force permanently. Other tax provisions in the measure include the elimination of federal taxation of tips and overtime.

The CBO estimate stands in stark contrast to the projection of the White House Council of Economic Advisers (CEA), which projects the OBBB will spark an economic boom, with the gross domestic product (GDP) going up by 4.6% to 4.9% within the next four years.

The difference between those two projections is essentially a function of the underlying assumptions used in each. A growing chorus of CBO critics contend the agency’s “static forecasts” always underestimate the positive, or “dynamic” impact of tax cuts on economic growth, government revenues, employment, and social welfare costs.

Matt Dickerson, director of Budget Policy at the Economic Policy Innovation Center (EPIC), told The Washington Stand that the CBO is a bureaucracy that too often tells favored politicians in Congress what they want to hear instead of what they should hear based on facts.

“The CBO is very good as a bureaucratic agency, and they will answer the question that is asked of them. And so, when the Democrats ask them a question, the things the Democrats ask for, CBO is going to give them. You ask the right question, you get the answer you want,” Dickerson said.

E.J. Antoni, chief economist for the conservative think tank The Heritage Foundation, told TWS that a major part of the problem with CBO is that Congress itself too often instructs the agency’s forecasters on how they do the work, the factors they consider, and the relative weights assigned to each of those factors.

“Congress sets up all of these crazy rules that CBO has to follow, and so it essentially becomes garbage in-garbage out,” Antoni said. “There is a reason why the CBO numbers are always so off. There is a reason why they are always so biased against things like tax cuts and for things like spending increases. Congress has set it up in just such a way.”

Antoni said that in addition to consistently underestimating the “dynamic revenue effects of tax cuts,” CBO also “consistently underestimates the cost overrun effects that come from additional spending.” He also expressed frustration, wondering “why on Earth when Democrats are in charge [do] they make all the changes they want to get the kind of scoring they want, and when Republicans are in charge they typically don’t change anything?”

Merkley’s release of the CBO response to his request regarding the impact of the OBBB on federal deficits and debt comes against a curious backdrop in which Capitol Hill Republicans are rewarding CBO with a bigger budget in 2026. The House version of the Legislative Branch Appropriation Act of 2026 ups CBO funding by $20 million, while the Senate version’s hike is $2 million. A conference committee will have to work out a compromise on the specific figure.

But the same legislation in the House imposes a 48% budget cut on the Government Accountability Office (GAO), the “investigative arm of Congress.” The Senate version keeps GAO at its present spending level of $812 million.

The CBO’s forecasts on the OBBB have consistently projected increased deficits and debt-service costs, a pattern that critics contend has characterized the agency’s work whenever a major tax cut proposal is advanced by a Republican president or member of Congress. By contrast, GAO angered Trump earlier this year by filing litigation against some of his attempts to impound previously appropriated funds for programs like Head Start. The House responded to Trump’s anger, while the Senate did not.