By Paul Krugman.

So the Supreme Court — defying many expectations — upheld the Affordable Care Act, a k a Obamacare. There will, no doubt, be many headlines declaring this a big victory for President Obama, which it is. But the real winners are ordinary Americans — people like you.

How many people are we talking about? You might say 30 million, the number of additional people the Congressional Budget Office says will have health insurance thanks to Obamacare. But that vastly understates the true number of winners because millions of other Americans — including many who oppose the act — would have been at risk of being one of those 30 million.

So add in every American who currently works for a company that offers good health insurance but is at risk of losing that job (and who isn’t in this world of outsourcing and private equity buyouts?); every American who would have found health insurance unaffordable but will now receive crucial financial help; every American with a pre-existing condition who would have been flatly denied coverage in many states.

In short, unless you belong to that tiny class of wealthy Americans who are insulated and isolated from the realities of most people’s lives, the winners from that Supreme Court decision are your friends, your relatives, the people you work with — and, very likely, you. For almost all of us stand to benefit from making America a kinder and more decent society.

But what about the cost? Put it this way: the budget office’s estimate of the cost over the next decade of Obamacare’s “coverage provisions” — basically, the subsidies needed to make insurance affordable for all — is about only a third of the cost of the tax cuts, overwhelmingly favoring the wealthy, that Mitt Romney is proposing over the same period. True, Mr. Romney says that he would offset that cost, but he has failed to provide any plausible explanation of how he’d do that. The Affordable Care Act, by contrast, is fully paid for, with an explicit combination of tax increases and spending cuts elsewhere.

So the law that the Supreme Court upheld is an act of human decency that is also fiscally responsible. It’s not perfect, by a long shot — it is, after all, originally a Republican plan, devised long ago as a way to forestall the obvious alternative of extending Medicare to cover everyone. As a result, it’s an awkward hybrid of public and private insurance that isn’t the way anyone would have designed a system from scratch. And there will be a long struggle to make it better, just as there was for Social Security. (Bring back the public option!) But it’s still a big step toward a better — and by that I mean morally better — society.

Which brings us to the nature of the people who tried to kill health reform — and who will, of course, continue their efforts despite this unexpected defeat.

At one level, the most striking thing about the campaign against reform was its dishonesty. Remember “death panels”? Remember how reform’s opponents would, in the same breath, accuse Mr. Obama of promoting big government and denounce him for cutting Medicare? Politics ain’t beanbag, but, even in these partisan times, the unscrupulous nature of the campaign against reform was exceptional. And, rest assured, all the old lies and probably a bunch of new ones will be rolled out again in the wake of the Supreme Court’s decision. Let’s hope the Democrats are ready.

But what was and is really striking about the anti-reformers is their cruelty. It would be one thing if, at any point, they had offered any hint of an alternative proposal to help Americans with pre-existing conditions, Americans who simply can’t afford expensive individual insurance, Americans who lose coverage along with their jobs. But it has long been obvious that the opposition’s goal is simply to kill reform, never mind the human consequences. We should all be thankful that, for the moment at least, that effort has failed.

Let me add a final word on the Supreme Court.

Before the arguments began, the overwhelming consensus among legal experts who aren’t hard-core conservatives — and even among some who are — was that Obamacare was clearly constitutional. And, in the end, thanks to Chief Justice John Roberts Jr., the court upheld that view. But four justices dissented, and did so in extreme terms, proclaiming not just the much-disputed individual mandate but the whole act unconstitutional. Given prevailing legal opinion, it’s hard to see that position as anything but naked partisanship.

The point is that this isn’t over — not on health care, not on the broader shape of American society. The cruelty and ruthlessness that made this court decision such a nail-biter aren’t going away.

But, for now, let’s celebrate. This was a big day, a victory for due process, decency and the American people.