The Senate would likely need 60 votes to overcome Democratic opposition and pass key portions of the GOP health care bill under the chamber’s rules, a blow to both the plan’s policy and its political fortunes unless Senate Republicans are willing to break decades of precedent or the bill is substantially rewritten.

The Senate’s so-called “Byrd Rule” is designed to make sure policies passed under “budget reconciliation” — which allows legislation to advance with only 51 votes instead of the usual 60 needed to get past a filibuster — directly affect the federal budget, either by decreasing spending or by increasing revenue. (Vox has explained the Byrd Rule in great detail.)

The findings of the Senate parliamentarian, who evaluates whether policies included in bills meant to pass through reconciliation comply with the Senate rules, were posted online late Friday afternoon and sent out by Democratic ranking member Sen. Bernie Sanders’s office. A Senate Republican aide noted that the parliamentarian reviewed a draft version of the bill, and the legislation could still be changed.

They are a critical blow to Republicans’ hopes of repealing and replacing Obamacare. Their plan is already short on votes, but Friday’s news could make it even more difficult for Senate leaders to sway their holdouts.

The biggest casualty would be the GOP’s replacement for Obamacare’s individual mandate, which required people to buy insurance or face a penalty. Under the Senate GOP’s bill, people who went more than a month without health coverage and then bought insurance later on would have to wait six months for their coverage to take effect and cover their medical bills.

The provision was considered necessary in order to encourage people to sign up for health insurance and keep the market stable. Without such a provision, experts fear the insurance market could be sent into a death spiral — only the sickest people, who cost insurers the most, buy coverage, and premiums and costs continue to rise.

Another key provision for market stability — the funding of Obamacare’s cost-sharing reductions, currently in limbo because of an ongoing Republican lawsuit — was also said to be out of order under the Senate rules, according to a summary posted on the Senate Budget Committee website. The cost-sharing reductions are payments to insurers that help them meet a requirement that low-income people get help with their copays and deductibles.

Two provisions crucial for social conservatives, the defunding of Planned Parenthood and the restrictions on federal tax subsidies paying for health insurance that covers abortion, would also require 60 votes to overcome a filibuster and pass — and with no Democrats willing to vote for them, those provisions appear effectively dead. Without them, it could be even harder to win conservative support for the bill.

There have long been questions about whether changes to insurance regulations, like the waiting period, would comply with the rule. The Senate parliamentarian, Elizabeth MacDonough, appears to have sided with outside experts who believed they would not.

The parliamentarian did not evaluate a proposal by Sen. Ted Cruz that would allow health insurers to sell plans that do not comply with Obamacare’s regulations as long as they also sold plans that did. The provision is considered essential for conservative support, but outside experts are skeptical it satisfies the Byrd Rule. The proposal had not yet been added to the draft bill that the parliamentarian reviewed.

Republicans could try to override the parliamentarian’s findings while the bill is debated on the Senate floor, but that would require 60 votes. Democrats are almost certain not to side with Republicans against the parliamentarian in order to add these critical provisions back into the bill.

The other possibility is known as the nuclear option. The parliamentarian technically offers only guidance on which policies comply with the Byrd Rule and which ones do not; the chair — which in this case could be Vice President Mike Pence — makes the final decision.

But for decades, the parliamentarian’s judgment has been final. Some senators, particularly the most conservative members, have pushed for Republicans to sidestep the parliamentarian if she nixes key parts of their plan. But senior Republicans have balked, fearing the precedent it would set for the reconciliation process.