On Monday night, senators Jerry Moran of Kansas and Mike Lee of Utah announced that they would not support the Better Care Reconciliation Act, the Senate’s attempt to replace the Affordable Care Act. Without their votes, Senate Majority Leader Mitch McConnell is shy of the fifty he needs. So instead, McConnellwith President Trump’s encouragement on Twitterannounced a new play: the Senate will now take up the bill the House passed in May (the one Trump called “mean”) and amend it to instead be a repeal of Obamacare that will take effect in two years, “to provide for a stable transition period.”

This is the same bill the Senate passed in 2015 and President Obama vetoed; in essence, McConnell is daring Republicans to vote against something they previously supported now that it counts.

But they probably will anyway. Repealing the ACA without a replacement would immediately destabilize the health care market, which would be suicidal for their election prospects next year. After all, insurers have seen the GOP try and fail to develop an alternative to Obamacare for seven years. Why would they bet that another two years would do the trick?

But if this gambit did somehow work, what would the effects be? The Congressional Budget Office has an answer. In a word: disaster. Here are five things you need to know from the CBO’s January analysis.

1. This isn’t a full Obamacare repeal. The ACA’s regulations on things like essential health benefits and preexisting conditions would stay intact, because changing those would require an unattainble sixty votes in the Senate. Instead, this would eliminate subsidies and taxes and erase funding for Medicaid expansion.

2. Eighteen million people would lose insurance in the first year. After the Medicaid expansion went away, that number would increase to twenty-seven million. By 2026, thirty-two million additional Americans would be without health insurance. (The number of uninsured people would actually be lower if the insurance reforms passed as part of the ACA were also repealed.)

3. Health care would quickly become unaffordable anyway. Premiums in the marketplace will increase 20–25 percent in the first year, relative to the ACA. After Medicaid expansion ended, they would shoot up by 50 percent. By 2026, they would nearly double.

4. Insurers would flee the individual marketplace. According to the CBO, “the factors exerting upward pressure on premiums and downward pressure on enrollment in the [individual] market would lead to substantially reduced participation by insurers and enrollees in many areas. … About half of the nation’s population lives in areas that would have no insurer participating in the [individual] market in the first year after the repeal of the marketplace subsidies took effect, and that share would continue to increase, extending to about three-quarters of the population by 2026.”

5. Some conservative senators have SAID repealing the ACA without a replacement IS A TERRIBLE IDEA. In January, Senator Tom Cotton of Arkansas said that “when we repeal Obamacare, we need to have the solution in place. … I do not think we can just repeal Obamacare and say we’ll give the answer two years from now.” Rand Paul: “If Congress fails to vote on a replacement at the same time as repeal, the repealers risk assuming the blame for the continued unraveling of Obamacare.” Bob Corker: “[It] would be best for our country to go ahead and replace it with something that works and repeal at the same time.”