When the Obama administration announced in October that premiums would rise by 25 percent on average for midlevel plans on the federal exchanges, Republicans predicted that this would doom the system. They ignored the fact that most people would not have to pay more because federal subsidies would rise to account for the higher premiums charged by private insurers. About 77 percent of people eligible for the coverage on the exchanges can find policies for $100 a month or less.

Still, the cost of insurance, deductibles and co-payments is too high for many people, especially middle-class families that earn too much to qualify for subsidies. But the solution is not to take away the benefits of the law but to strengthen it. Costs could be lowered if more young and healthy people were encouraged to sign up to spread costs over a larger pool of people.

There is growing evidence that the law is working in other ways, too. The proportion of people who did not see a doctor because they couldn’t afford to fell by at least two percentage points between 2013 and 2015 in 38 states and the District of Columbia, according to a new study by the Commonwealth Fund. That helps explain why only a quarter of Americans surveyed by the Kaiser Family Foundation said the law should be scrapped.

If lawmakers are moved by nothing else, they should think about the political costs of repealing the Affordable Care Act or crippling it with piecemeal changes. Many of the people who benefit from health reform live in states that voted for Mr. Trump and down-ballot Republicans. The Kaiser foundation estimated that residents of Florida received $5.2 billion in subsidies to buy health insurance as of last March, more than in any other state. More than 600,000 people in Ohio are enrolled in Medicaid thanks to the law. And in Texas, there are 4.5 million people with pre-existing conditions who cannot be denied coverage under the law, or charged higher prices.

Treating the Affordable Care Act as a punching bag during a political campaign is one thing. But it is quite another to destroy a law that is helping so many people.