WHAT IF we told you that there was a plan that, unlike so many recent Republican health-care bills, could reform the health-care system and restrain costs without kicking anyone off their coverage? In fact, that bill exists, the Congressional Budget Office confirmed on Wednesday. The bipartisan compromise proposal crafted by Sens. Lamar Alexander (R-Tenn.) and Patty Murray (D-Wash.) now officially falls into the category of "so obvious it should pass immediately."

The motivation for the Alexander-Murray compromise was President Trump's reckless refusal to distribute cost-sharing reduction payments to insurance companies — money the government promised insurers in exchange for participating in Obamacare. The CBO had previously warned that ending the payments would actually cost the government $194 billion over 10 years, because it would force other federal programs to pay out more in subsidies to consumers in the individual health-insurance market. Mr. Trump ignored this warning.

The Alexander-Murray bill would restore the payments for two years. The CBO predicts that, though the damage has been done for 2018, the bill would restrain premiums and cut government spending in 2019. If the payments were continued beyond that point, the savings would presumably continue, as well.

But the Alexander-Murray plan contains much more, and the CBO's findings on the bill's Obamacare reforms are the most illuminating pieces of the new analysis. For example, the bill would allow all people to buy "copper" (as opposed to gold, silver or bronze) health-care plans, which would offer consumers less generous benefits at a lower monthly price. The CBO found that this provision would draw more healthy people into the individual market, lowering average premiums and saving the government $1 billion. Streamlining the process though which states can obtain waivers from Obamacare rules, meanwhile, would spur more state-based experimentation.

These selling points, however, may not change Republican thinking, at least not judging by GOP leaders' behavior. HuffPost reported Tuesday that House Speaker Paul D. Ryan (R-Wis.) told conservative lawmakers that the Alexander-Murray plan probably would not be attached to a year-end budget package, the most likely vehicle for its passage. Mr. Trump has been all over the map on the compromise, seeming to encourage the deal at one point, and then, at another, demanding absurd new concessions that Democrats would never accept. Sen. Orrin G. Hatch (R-Utah) and Rep. Kevin Brady (R-Tex.) on Tuesday released their own, more conservative version that calls for dismantling major pieces of Obamacare — an unhelpful, partisan proposal that would hurt health-care markets, cannot pass and makes real compromise more difficult.

Republicans can continue ignoring reality, tempting chaos in health-care markets and risking the nation's fiscal health. But they cannot claim they were not warned.