Mitch McConnell has a brand-new headache after Senate parliamentarian Elizabeth MacDonough tore up several key provisions of the pending Trumpcare bill on procedural grounds. Photo: Melina Mara/The Washington Post/Getty Images

In a major, and perhaps fatal, blow to any version of Trumpcare, Senate parliamentarian Elizabeth MacDonough has excluded several key features of the latest bill to repeal and replace Obamacare as items that cannot be enacted under the filibuster-immune special-budget rules.

In an explanatory document released late Friday by the Senate Budget Committee, a number of provisions have run afoul of the parliamentarian’s so-called “Byrd Bath,” a review (named after the late Sen. Robert Byrd) designed to ensure that budget bills stick to dictates that have an impact on the budget.

On the wonky side of the ledger, the big blow is the exclusion of a provision called the “Six-Month Lock Out,” a measure imposing a waiting period for people applying for initial individual insurance policies. This was the GOP’s replacement for the hated individual mandate, which was Obamacare’s mechanism for discouraging younger and healthier people from waiting to buy insurance until they actually needed it. Without it, the system set up by Trumpcare could unravel via a “death spiral” as individual-insurance risk pools are increasingly dominated by less healthy people.

Politically, though, the bigger problem is the parliamentarian’s exclusion of two provisions dealing with abortion: a one-year ban on any federal funding for Planned Parenthood and a separate prohibition on use of health-care-purchasing tax credits to obtain a policy with abortion coverage. The latter provision was always a little questionable on Byrd Rule grounds, but the former was thought to be less of a problem, since it was included in the 2015 bill repealing Obamacare (subsequently vetoed by President Obama).

There is no way the anti-abortion advocates who are a powerful force in the Republican Party will support passage of a bill without either of these provisions attached — unless they are somehow given a different option not subject to a Democratic filibuster, which will be very hard to find. The repercussions go beyond the Senate, too: House Freedom Caucus chair Rep. Mark Meadows is already tweeting that the exclusions will make “passage almost impossible.”

And so, it appears Republicans will be forced to choose between abandoning their health-care legislation and taking the extremely risky approach of overruling the parliamentarian on the Senate floor — a tack that could lead to a virtual abolition of the legislative filibuster, since a Senate majority could henceforth place any legislation it wanted under the special simple-majority rules applying to budget bills. Ted Cruz has been pushing for this “solution” all year, but it’s one Mitch McConnell, self-appointed conservator of Senate traditions, has been reluctant to embrace.

Speaking of Cruz, the parliamentarian’s rulings all involved the June 26 version of the Senate Trumpcare bill, and thus did not include the Texas senator’s controversial amendment allowing insurers to offer cheap and less comprehensive individual policies — one of the keys to conservative support for the latest version of the bill. If the Cruz Amendment is included in the bill actually offered by Mitch McConnell, it could be challenged on the Senate floor for Byrd Rule compliance, and no one knows what would happen then.

In general, the parliamentarian has taken an already very difficult process for enacting health-care legislation in the Senate and made it nearly impossible — unless Mitch McConnell is willing to blow up every Senate precedent without even knowing if it would be enough to persuade 50 senators from his own party. It will be a painful weekend for those whose dreams involve the repeal or replacement of Obamacare.