By Paul Krugman — New York Times.

A message to progressives: By all means, hang Senator Joe Lieberman in effigy. Declare that you’re disappointed in and/or disgusted with President Obama. Demand a change in Senate rules that, combined with the Republican strategy of total obstructionism, are in the process of making America ungovernable.

But meanwhile, pass the health care bill.

Yes, the filibuster-imposed need to get votes from “centrist” senators has led to a bill that falls a long way short of ideal. Worse, some of those senators seem motivated largely by a desire to protect the interests of insurance companies — with the possible exception of Mr. Lieberman, who seems motivated by sheer spite.

But let’s all take a deep breath, and consider just how much good this bill would do, if passed — and how much better it would be than anything that seemed possible just a few years ago. With all its flaws, the Senate health bill would be the biggest expansion of the social safety net since Medicare, greatly improving the lives of millions. Getting this bill would be much, much better than watching health care reform fail.

At its core, the bill would do two things. First, it would prohibit discrimination by insurance companies on the basis of medical condition or history: Americans could no longer be denied health insurance because of a pre-existing condition, or have their insurance canceled when they get sick. Second, the bill would provide substantial financial aid to those who don’t get insurance through their employers, as well as tax breaks for small employers that do provide insurance.

All of this would be paid for in large part with the first serious effort ever to rein in rising health care costs.

The result would be a huge increase in the availability and affordability of health insurance, with more than 30 million Americans gaining coverage, and premiums for lower-income and lower-middle-income Americans falling dramatically. That’s an immense change from where we were just a few years ago: remember, not long ago the Bush administration and its allies in Congress successfully blocked even a modest expansion of health care for children.

Bear in mind also the lessons of history: social insurance programs tend to start out highly imperfect and incomplete, but get better and more comprehensive as the years go by. Thus Social Security originally had huge gaps in coverage — and a majority of African-Americans, in particular, fell through those gaps. But it was improved over time, and it’s now the bedrock of retirement stability for the vast majority of Americans.

Look, I understand the anger here: supporting this weakened bill feels like giving in to blackmail — because it is. Or to use an even more accurate metaphor suggested by Ezra Klein of The Washington Post, we’re paying a ransom to hostage-takers. Some of us, including a majority of senators, really, really want to cover the uninsured; but to make that happen we need the votes of a handful of senators who see failure of reform as an acceptable outcome, and demand a steep price for their support.

The question, then, is whether to pay the ransom by giving in to the demands of those senators, accepting a flawed bill, or hang tough and let the hostage — that is, health reform — die.

Again, history suggests the answer. Whereas flawed social insurance programs have tended to get better over time, the story of health reform suggests that rejecting an imperfect deal in the hope of eventually getting something better is a recipe for getting nothing at all. Not to put too fine a point on it, America would be in much better shape today if Democrats had cut a deal on health care with Richard Nixon, or if Bill Clinton had cut a deal with moderate Republicans back when they still existed.

But won’t paying the ransom now encourage more hostage-taking in the future? Maybe. But the next big fight, over the future of the financial system, will be very different. If the usual suspects try to water down financial reform, I say call their bluff: there’s not much to lose, since a merely cosmetic reform, by creating a false sense of security, could well end up being worse than nothing.

Beyond that, we need to take on the way the Senate works. The filibuster, and the need for 60 votes to end debate, aren’t in the Constitution. They’re a Senate tradition, and that same tradition said that the threat of filibusters should be used sparingly. Well, Republicans have already trashed the second part of the tradition: look at a list of cloture motions over time, and you’ll see that since the G.O.P. lost control of Congress it has pursued obstructionism on a literally unprecedented scale. So it’s time to revise the rules.

But that’s for later. Right now, let’s pass the bill that’s on the table.