There’s a curious movement afoot from a certain section of the liberal ecosystem, reacting very strongly to disappointed and frustrated elements of the progressive base, and exhorting everyone to “pass the bill,” despite whatever provisions it lacks. This is happening not only among certain bloggers like Ezra Klein and Matt Yglesias, but several liberal opinion leaders, most notably Paul Krugman.

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.

It would be wrong to dismiss Krugman completely. There is a lot of good in the Senate bill. I could rattle off a dozen positive developments – insurance regulations banning rescissions and pre-existing conditions, coverage expansions with hundreds of billions in associated subsidies, the ending of gouging the uninsured for ER visits, expanding community health centers, delivery system reforms, etc. Henry Aaron has a lot more on this in the Washington Post today.

What is wrong is trying to browbeat progressives into “passing the bill” (as if we have a vote) when, um, the bill isn’t done! And what this does, this concentrated effort to pass something, anything, is enable people like Ben Nelson, who aren’t entirely interested in health care to begin with, to extract another round of compromises, which would have a horrible real-world effect.

Earlier Thursday, in an interview with a Nebraska radio station, Nelson said even if the abortion issue were resolved, he still could not support the $848 billion package, complaining that the plan to cover more than 30 million additional Americans calls for dramatically expanding Medicaid, which is partially funded by the states. The Medicaid expansion would “create an underfunded federal mandate for the state of Nebraska,” Nelson said, arguing that states should be permitted to “opt out” of that idea and find other ways to offer coverage to their poorest residents.

Medicaid expansion is the single most successful part of the bill, as Jon Walker acknowledges. It’s responsible for nearly half of the coverage expansion in the bill, and at a lower cost than subsidies. And let’s be clear, Nelson is completely wrong about the unfunded mandate – for the first three years, the government pays 100% of the coverage expansion, and over 90% thereafter. And Medicaid offers better coverage than the junk insurance coverage that can be offered at the low end of the affordability scale, the most likely coverage that poor people in this income bracket would accept.

At what point does the “pass the bill” rhetoric become enabling for Nelson to pull this nonsense before the bill is complete, making any talk about passing the bill utterly premature?

Some of the liberal arguments against the bill may not be well-founded, though I think many of them are. But by and large, liberal unhappiness is focused on getting to a better bill and not being absolutist. Shutting down that process, and saying “anyone would be crazy” not to pass what the Senate puts out, just helps Ben Nelson work his magic. It signals a willingness to let the bill be totally eviscerated, and still work to pass it in the name of “reform.”

It’s a poor strategy.

UPDATE: Hey, Jim Webb’s undecided too. I think before this is over, even Reid will be undecided to see what he can get from himself.