WASHINGTON — President Trump and House Republicans on Thursday took a big step toward fulfilling their promises to repeal the Affordable Care Act, narrowly passing a bill that would end the law’s mandates and taxes and also endanger coverage for millions of Americans by sharply cutting Medi-caid spending.

The Republicans’ repeal bill passed 217 to 213, six weeks after a previous effort to force the legislation through ended in a humiliating collapse. Not a single Democrat voted for the bill, while 20 Republicans opposed it.

The measure heads to the Senate, where it probably cannot pass in its current form, posing further tests for the fractured GOP to demonstrate it can translate one-party control in Washington into action.

In a highly unusual display, Trump bused House Republicans over for a victorious press conference in the Rose Garden after the vote — the sort of back-slapping photo opportunity usually reserved for the signing of actual laws, as opposed to the passage of still-unfinished legislation. At the Capitol, cases of celebratory beer were spotted being wheeled through the corridors.

The Affordable Care Act “has been a catastrophe, and this is a great plan,’’ Trump said, predicting that health insurance premiums and deductibles would start to fall. “We won, and we’re going to finish this off.’’

But in delivering on the key promise of eliminating the Affordable Care Act’s mandates and slashing its subsidies, the legislation also breaks prominent pledges Trump made both as a candidate and as president.

It would slash federal spending on Medicaid by $800 billion, despite Trump’s promises on the stump not to touch the federal health insurance program for the poor if he won the election. It also would drastically weaken protections for people with preexisting conditions, contrary to other repeated promises.

Estimates of an earlier version of the bill said it would result in 24 million Americans losing health insurance. House leaders rammed the new bill through so hastily that there was no new estimate from the nonpartisan Congressional Budget Office of how many people would lose insurance or what the effect on the federal budget would be.

Despite suffering a crucial loss in their efforts to protect former president Barack Obama’s signature law, Democrats seemed almost gleeful as the vote was tallied because of the political ammunition they believe it gives them for the 2018 and 2020 elections.

Democrats gathered on the floor started singing “Hey, hey, hey! Goodbye!’’ and some taunted their Republican colleagues with waves as the health care bill crossed the necessary vote threshold. “Last chance!’’ a few called out before the vote was gaveled closed and lawmakers could no longer change their votes.

“You have every provision of this bill tattooed on your forehead. You will glow in the dark on this one,’’ House minority leader Nancy Pelosi warned her GOP colleagues in a floor speech.

The bill also was opposed by virtually all health care lobbying groups, including those representing hospitals, doctors, and patients.

Republican leaders celebrated it as a victory that would pull the nation’s health care system back from the brink of disaster and give consumers more choices and lower costs.

“This bill delivers on the promises we have made to the American people,’’ House Speaker Paul Ryan said in his own floor speech. “A lot of us have been waiting seven years to cast this vote.’’

The bill would eliminate the “individual mandate’’ that requires that all Americans either purchase insurance or pay a tax penalty. States that want to continue with their own mandates would be allowed to, like Massachusetts — which pioneered the mandate concept under former governor Mitt Romney. But federal money to subsidize insurance coverage for those required to buy it would be substantially reduced.

The bill aims to accomplish other major Republican ideological goals, including capping overall federal spending on Medicaid, a dramatic change that would stop costs from growing in the open-ended entitlement program. But Democrats argued that the cuts will simply shift costs onto states, the sick, and the elderly.

The biggest pivot point in the legislation this week was the fate of an Affordable Care Act provision that prevents insurance companies from denying coverage, or charging higher premiums, for people with preexisting conditions like cancer, diabetes, or high blood pressure.

Despite Trump’s support of that provision as recently as Monday, Ryan and the House leadership agreed to allow states to opt out of that part of the current law. States that make that choice will have an additional $8 billion in federal support for publicly run “high risk pools’’ to cover sick patients.

The bill also eliminates requirements that insurance policies cover various maladies including mental illness and addiction. And opponents said it allows insurance companies to return to practices in which treatments for sexual assault and pregnancy were considered preexisting conditions.

The changes could usher in the return of the type of insurance horror stories that drove passage of the law in the first place — families facing bankruptcy or the unnecessary death of loved ones after being denied coverage because of a preexisting condition.

Already the health care issue has skyrocketed to the top of the popular consciousness with the help of late-night host Jimmy Kimmel, who this week tearfully shared the story of his newborn son’s congenital heart defect and the fact that before the Affordable Care Act, there was a good chance his son would have been denied insurance. “No parent should ever have to decide if they can afford to save their child’s life,’’ he said.

Republicans promised their bill would still protect those with preexisting conditions. A leading moderate Republican, Tom MacArthur of New Jersey, who brokered the changes with conservative lawmakers, said the high-risk pools run by states would serve as a safety net.

The bill as revised makes “crystal clear that coverage for preexisting conditions is an absolute,’’ MacArthur said.

By preventing insurance companies from boosting premiums for people who were already sick, the Affordable Care Act took the most expensive risks “and put them on the shoulders of other policy holders,’’ making everyone’s premiums skyrocket and leaving millions unable to afford insurance, MacArthur said. “The solution in this bill is to take the most expensive risks and put them on the much broader shoulders of the entire American taxpayer.’’

But experts across the political spectrum say the money provided in the bill to fund those high-risk pools and similar efforts falls far short of what the actual costs will be. In total, with the additional $8 billion, the bill provides $138 billion to help states cover costs for those with serious illnesses via high-risk pools.

Moderate Republicans who voted against the bill expressed dismay with the House GOP approach to health care.

“I am disappointed that the House passed this bill, which I believe will increase health insurance costs — particularly for low-to-moderate income Americans,’’ said Pennsylvania GOP Representative Charlie Dent, a moderate.

Representative Ileana Ros-Lehtinen, a Republican who recently announced she would not run for reelection to her Miami-area seat, was even harsher. “I will not support a bill that has the potential to severely harm the health and lives of people in South Florida,’’ she announced ahead of the vote. “My constituents should not have to take a step backward in their ability to obtain treatment for any illness.’’

House minority whip Steny Hoyer predicted Ryan would find his legislative victory Thursday short-lived. “It is a bill that he is going to have to be struggling to answer for, for the balance of this Congress, and I think is going to hurt him in the next election,’’ the Maryland Democrat said.

“It’s devastating for Massachusetts. It’s devastating for those who need access to health care,’’ said Massachusetts Representative Joseph Kennedy III, who emerged as an emotional voice of opposition during debate on the bill.

He called the prospect of treatment for sexual assault being a preexisting condition — thereby endangering insurance coverage “stunning to me. Stunning.’’

In the Senate, Democrats appear united in their opposition, and more than a few Republicans have expressed deep reservations about the thrust of the House measure.

Senate majority leader Mitch McConnell plans to use a special procedural tactic to avoid the filibuster, and thus the need for any Democratic votes, to pass health care legislation with a simple majority of 51 votes. The approach means he can only lose two GOP senators. To keep moderate Republicans on board, the Senate bill is likely to be drastically changed from the House version.

“You’re walking the plank for what?’’ Pelosi asked her GOP colleagues before the vote. “A bill that will not be accepted by the United States Senate. Why are you doing this?’’

Victoria McGrane can be reached at victoria.mcgrane@globe.com. Follow her on Twitter @vgmac.