You Know Who was back on Twitter Thursday morning, and for the second day running he addressed the Republican effort to repeal the Affordable Care Act—a venture that is already threatening to turn into a political disaster for the G.O.P., and a much-needed lifeline for the Democrats.

“The Democrats, lead by head clown Chuck Schumer, know how bad ObamaCare is and what a mess they are in,” President-elect Donald Trump said, in a series of tweets. “Instead of working to fix it, they . . . do the typical political thing and BLAME. The fact is ObamaCare was a lie from the beginning. ‘Keep you doctor, keep your plan!’ It is . . . time for Republicans & Democrats to get together and come up with a healthcare plan that really works—much less expensive & FAR BETTER!”

In parsing this latest Trump outburst, a bit of context helps. During the Presidential campaign, Trump adopted the standard Republican line on the Affordable Care Act—that it was a mess that needed replacing—even as he also expressed support for some of the law’s provisions, such as the one that prevents insurers from shunning people with preëxisting conditions. Since the election, however, two things that should already have been obvious have become impossible to ignore, even for Trump. For one thing, neither he nor the Republican Party has a viable replacement to offer for the A.C.A. And congressional Democrats, led by Chuck Schumer, the new Senate Minority Leader, have no intention of helping them out.

On Wednesday morning, Schumer, also on Twitter, said, “Republicans should stop clowning around with America’s health care. Don’t #MakeAmericaSickAgain.” Schumer’s jab coincided with a visit to Capitol Hill by Mike Pence, the Vice-President-elect, during which Pence said that repealing and replacing the A.C.A. was the incoming Administration’s first order of business. As an initial step, Senate Republicans, who have an effective majority of four seats in the new chamber, recently passed a procedural resolution that could enable them to repeal key parts of the A.C.A. with just fifty-one votes, thereby avoiding a Democratic filibuster.

This means a number of key elements of the law could be demolished, or slated for demolition. They include the employer and individual mandates; the federal subsidies for insurance policies purchased on government-run exchanges; the expansion of Medicaid to households that are living slightly above the poverty line; and the taxes on wealthy households that were imposed to help pay for the reform. Republican leaders are considering pushing through legislation to gut Obamacare of these components straight away, but delaying implementation for a period—perhaps two or three years—while they devise a new system to replace it.

The problems with this “repeal and delay” strategy are obvious and unavoidable. Once the repeal legislation was passed, more than twenty million Americans would face the prospect of losing their health-care coverage. (This figure comes from the nonpartisan Congressional Budget Office, which analyzed the likely impact of an anti-Obamacare bill that Republicans passed in 2015, which President Obama vetoed.)

Most of those who would lose out would be individuals and families of modest means, many of them living in the blue or blue-ish states that expanded Medicaid under the law. (Many red states refused to accept the Medicaid expansion.) A cynical student of history might suggest that the Republican Party could afford to ignore these blue-state folks. But the socioeconomic base of the G.O.P. has shifted, and, according to a back-of-an-envelope calculation by Paul Krugman, about 5.5 million of the victims of repealing the A.C.A. would be Trump supporters. In many parts of the country, large numbers of white households subsist on incomes low enough to make them eligible for Medicaid or hefty subsidies to buy private insurance. We didn’t hear much from this group during the campaign, but that would surely change if the Medicaid expansion and the subsidies were both eliminated.

In addition to harming large numbers of Trump voters, repealing most of the A.C.A. would enrage some rich and powerful economic interests that the Republican Party has traditionally courted, such as doctors, hospitals, and insurers. It took the American health-care industry, which is now bigger than the entire economy of France, half a decade to prepare for and implement the law’s provisions. Many working in health care believe it would be folly to destroy the new system before building a proper replacement.

Insurers are warning that a “repeal and delay” plan would create immediate turmoil on the government-run exchanges, many of which are already having trouble attracting more than one or two insurers to participate. Last month, two big trade groups—the American Hospital Association and the Federation of American Hospitals—warned publicly that repealing the A.C.A. could cost hospitals a hundred and sixty-five billion dollars and trigger an “unprecedented public health crisis.” In a letter to Congress on Tuesday, Dr. James Madara, the chief executive of the American Medical Association, said, “We believe that before any action is taken . . . policymakers should lay out for the American people, in reasonable detail, what will replace current policies.”

No wonder Trump is concerned. Having campaigned as an economic populist who would focus his efforts on jobs and trade, he now runs the risk of getting embroiled in a battle over health care that could conceivably overshadow everything else he does. “Some Republicans think they can repeal ObamaCare and blame Mr. Obama for the fallout, but they are kidding themselves,” the editorial page of the Wall Street Journal, which itself has been a vehement opponent of the A.C.A., noted on Thursday. “Republicans were elected on a promise to repeal and replace, and the statute of limitations on blaming Mr. Obama will soon expire.”

It’s looking more and more like the Republicans are caught in a trap of their own making. Ever since 2008, they and their media outriders, such as Rush Limbaugh and Sean Hannity, have demagogued the health-care issue in an outrageous fashion. Trump, in running for President, employed the same nihilistic strategy. Now they may pay for it. Despite the Republicans’ vague talk of stripping away government bureaucracy and setting up a more “market-based system” to replace Obamacare, there is no quick fix, no cheap way out. In a private health-care market, the only way to guarantee universal, or near universal, coverage is to employ mandates, subsidies, taxes, and legal directives—the very tools employed in the A.C.A.

At some point, presumably, the Trump Administration and the Republican leadership on Capitol Hill will cobble together some sort of proposal. In all likelihood, it will feature lower-quality insurance plans, large deductibles, and hefty payments to insurers to cover high-risk patients. But the congressional sponsors of such a plan could end up being held hostage by the same Democrats they have been tormenting for years. Even if the Republicans succeed in gutting the A.C.A. with fifty-one votes in the Senate, they will need sixty votes to pass a replacement, which means they will need help.

No wonder Schumer looks so chipper—a bit too chipper, perhaps, for someone whose party recently squandered an opportunity to win a majority. On Thursday morning, shortly after Trump’s latest Twitter barrage, the Brooklynite held a press conference, at which he stood next to a whiteboard with the words “MAKE AMERICA SICK AGAIN” emblazoned on it. Asked about Trump labelling him a clown, Schumer replied, “I’d say to the President-elect that this is serious, serious stuff. People’s health is at stake and people’s lives are at stake. . . . Instead of calling names, the President-elect should roll up his sleeves and show us a replacement plan.”