The Republican plan to replace the Affordable Care Act would leave 24 million more Americans without health insurance by 2026 than under current law, according to an analysis Monday from the Congressional Budget Office.
The CBO report found that 14 million more people would be without health insurance by 2018.
Following a two-year spike, the plan would also lower average premiums after 2020 relative to President Barack Obama's healthcare law. But premiums would be expected to go down for younger people, while being raised for older Americans.
The nonpartisan projection also estimates the GOP legislation would reduce federal deficits by $337 billion by 2026.
Democrats immediately pounced on the number of Americans who stand to lose insurance over the next decade, which was substantially higher than previous estimates.
"The CBO score shows just how empty the president's promises, that everyone will be covered and costs will go down, have been. This should be a looming stop sign for the Republicans repeal effort," Senate Minority Leader Chuck Schumer said in a statement. He later told reporters the results should be a "knockout blow" to GOP efforts to replace Obamacare.
House Speaker Paul Ryan, who has championed the bill, pointed to the CBO conclusion that the legislation will lower costs and reduce the deficit.
"This report confirms that the American Health Care Act will lower premiums and improve access to quality, affordable care. CBO also finds that this legislation will provide massive tax relief, dramatically reduce the deficit, and make the most fundamental entitlement reform in more than a generation," House Speaker Paul Ryan, who has championed the bill, said in a statement.
He also contended that the scoring did not take into account additional steps "that will further lower costs and increase choices." Ryan has said the bill examined by the CBO was just one step in a three-step process that includes Health and Human Services regulations and additional legislation.
Similarly, White House officials dismissed the conclusions of the report by arguing the agency took too narrow of a view when grading the legislation.
"We disagree strenuously with the report that was put out," Health and Human Services Secretary Tom Price told reporters gathered outside the White House.
White House Office of Management and Budget director Mick Mulvaney said the estimated lowered premiums are an example of "something the CBO may have gotten right."
Advocates of the legislation began bracing for bad news ahead of the CBO's release. The GOP plan's elimination of the government requirement to purchase insurance all but guaranteed the projection that fewer Americans would be covered.
"The one thing I'm certain will happen is CBO will say, 'Well, gosh, not as many people will get coverage.' You know why? Because this isn't a government mandate,'" House Speaker Paul Ryan said on CBS News on Sunday.
The Trump administration, which supports the plan, has argued that the CBO was ill-equipped to grade legislation with such a massive scope.
"I love the folks at the CBO, they work really hard. They do. Sometimes we ask them to do stuff that they're not capable of doing," Mulvaney said on ABC News on Sunday.
The projection only further complicates the already shaky chances the legislation passes. Democrats stand ready to pounce on GOP lawmakers for advocating for a plan that could lead to less Americans having health insurance. Conservative members of Congress, however, oppose the legislation for not quickly enough repealing the major tenets of Obama's healthcare law, like Medicaid benefits.
"I firmly believe that nobody will be worse off financially in the process that we're going through," Price said on NBC's "Meet The Press" on Sunday. "They'll have choices that they can select the kind of coverage that they want for themselves and for their family, not the government forces them to buy."