This week, Republicans in the House of Representatives passed a health-care bill that will hurt millions of Americans. They accomplished this feat by wrangling votes from hesitant moderates. But vulnerable members of Congress may soon find that they have gambled with innocent people’s lives for what amounts to a suicide mission.

To understand why, one must first consider Republicans’ strategy around repealing and replacing Obamacare. Because they hold a narrow 52-48 majority in the Senate, Republicans have planned on passing their health-care bill through the budget reconciliation process. Reconciliation was devised to make it easier to pass budgetary bills that do not increase the deficit. These bills can pass the Senate on a bare majority of 51 votes, instead of the 60 needed to beat back a filibuster.

Because Democrats will assuredly filibuster any attempt to repeal their signature legislative achievement, Republicans have been intent on crafting a health-care bill that they can shoehorn through Senate reconciliation. That’s why the GOP’s original health-care bill in March left much of Obamacare’s architecture in place, like its insurance regulations and protections for people with preexisting conditions. Republican leadership thought that repealing these parts of the law would not pass muster under reconciliation, because they do not directly affect federal spending. That bill triggered a revolt first by House conservatives, incensed that it resembled Obamacare-lite, and then by moderates, spooked by projections that the bill would strip coverage from 24 million people and send premiums soaring for the poor, sick, and old.

When Republicans regrouped this week, their new bill took aim at more of Obamacare, allowing states to opt out of the law’s regulations guaranteeing the benefits covered by every plan, and weakening Obamacare’s protections for people with pre-existing conditions. This won over conservatives. Moderates were brought on board through political pressure from their leadership and the White House, along with a pittance of $1.6 billion per year to help defray the crippling new costs people with pre-existing conditions could expect under the bill. That revised bill passed the House on Thursday.

The problem, however, is that the same changes in the bill that won over House conservatives may not survive the Senate’s reconciliation process. Weakening Obamacare’s essential health benefits and its protections for the sick are major policy changes, but they do not have a direct impact on the federal budget. Other provisions of the bill might also run afoul of reconciliation rules, including allowing insurers to charge higher premiums to older people and to impose a 30% premium markup on anyone who was previously uninsured.

Moreover, House Republicans rushed their new bill through the chamber before the Congressional Budget Office could assess its impact on spending and insurance coverage, sparing the moderates from reckoning with the human toll of their votes. However, the Senate cannot even consider whether a bill passes muster under reconciliation until receiving a CBO score. If that score is a bloodbath like the score of the first bill, the Senate may quickly retreat even further from the House bill.

The Senate is also unlikely to go along with the House’s plans to cut $800 billion from Medicaid and roll back Obamacare’s expansion of that program to poor and working-class people. Several Republican senators from Medicaid expansion states—like Rob Portman (R-Ohio), Shelley Moore Capito (R-W. Va.), Cory Gardner (R.-Colo.), and Tom Cotton (R.-Ark.)—have raised issue with the bill’s massive cuts to Medicaid. Because these senators could be the deciding votes, they will have substantial leverage to dictate the terms of the Senate bill.

At the same time, it will be hard to both restore Medicaid funding and retain the House’s $600 billion in tax cuts for the wealthy while still reducing the deficit, as required by reconciliation rules. Good luck with that juggling act.

All of which is to say that the House moderates rolled over to pass a bill that is essentially useless to the Senate. Indeed, the Senate is already rejecting the House bill out of hand, starting from scratch instead. Given the Republicans’ slim majority and the strictures of reconciliation rules, the Senate is likely to produce a bill that is at least somewhat less retrograde and devastating than the House bill, if it manages to produce anything at all.

Then the House will need to approve the more moderate Senate bill, and the tug-of-war between Republican moderates and hardliners will resume. The conservative House Freedom Caucus, emboldened after successfully dragging the House bill to the right, will be unlikely to back any bill that deviates too far from what the House passed. “[The Senate] better not change it one iota,” Freedom Caucus member David Brat (R-Va.) threatened. “If they change it, you’re not going to have 218 [votes].” If that’s true, then any bill the Senate produces may not be able to pass the House and make it to US president Donald Trump’s desk.

So there is a long, long way to go before Republicans succeed in repealing and replacing Obamacare, and many, many ways the whole endeavor can still fall apart. In the meantime, House Republican moderates are hung out to dry backing a devastating bill for no sure outcome. And if the Republican bill does manage to become law, the moderates will be culpable for the American carnage of sick people losing insurance and millions of people facing unaffordable health-care costs. As House Minority Leader Nancy Pelosi put it, “This is a scar that they’ll carry.”