The Congressional Budget Office, the legislative branch’s fiscal analysis agency, released an updated estimate of the One Big Beautiful Bill Act on Tuesday that Republicans will appreciate even less than the first. The CBO’s initial report from early June found that, excluding knock-on economic effects, President Trump’s signature legislative package, as passed by the House, would increase the national debt by $2.4 trillion over the next decade. The new report incorporates the previously missing macroeconomic impact on GDP growth, interest rates, and inflation, and finds that such factors would increase the debt by nearly $400 billion, raising the bill’s total cost to $2.8 trillion.

As Politico reports, congressional Republicans were hopeful that this “dynamic” estimate would revise the bill’s debt impact downward, as they anticipated that tax cuts would grow the economy enough to generate higher overall revenues. Yet the CBO calculates that the legislation would increase real GDP by just half a percentage point over ten years, thanks to a measly 0.04 percent boost in annual economic growth. The positive fiscal effects of this slightly larger U.S. economy would be swamped by higher payments to federal bondholders, as lowering taxes would put greater demand-side pressure on inflation, causing the Federal Reserve to keep interest rates higher than they otherwise would.

These findings will likely supply Democrats with more ammunition against the Republicans’ megabill, as they have grabbed onto previous CBO reports to attack the legislation’s overall cost and “distributional effects” on households. It may also add to a conundrum within Republicans’ own ranks. To provide cover for self-described deficit hawks, the House reconciliation framework assumed that the bill would raise yearly economic growth over a decade from the CBO’s projected 1.8 percent to a far brisker 2.6 percent. That extra expansion, the Budget Committee argued, would make the bill entirely deficit-neutral through higher revenues.

Just one problem: Not a single independent analysis comes anywhere close to matching Republicans’ rosy growth assumption. Accordingly, the consensus among budget experts is that the megabill will be anything but deficit-neutral, adding trillions of dollars to the national debt by 2034. This week’s dynamic estimate from the CBO further complicates this narrative just as fights within the Republican Party over the bill’s most fiscally consequential provisions — from Medicaid reform, to green energy subsidies, to the SALT deduction — are boiling over.