"This is the last, best shot." That's how one veteran policy wonk described the state of health care reform to me a few days ago. And that sounds about right.

On Monday morning, the White House will publish its final vision for health care reform. It will be a series of changes to the Senate bill, designed to accommodate both the concerns of the House and the concerns of the public more generally. (Among other things, it will include a new proposal to stop the sorts of rate hikes California's Blue Cross plan recently proposed.)

On Thursday, Obama will invite congressional leaders from both parties to Blair House for a half-day meeting. There, he will describe and advocate for his proposal, then offer Republicans to do the same. And that meeting may well be what decides what happens to reform.

There are, I suspect, three possible outcomes. One is an outbreak of genuine bipartisanship. It's by far the least likely of the options and not because Obama isn't interested. He and and his allies spent much of last year meeting with Republicans and crafting a bill that should have won support from the party's moderates.

But the Republican Party has no moderates anymore--or, at least, it has no moderates willing to vote that way. And so while I suspect Obama would (to my chagrin) embrace a scaled-down plan if a group of moderate Republicans offered one, my bet is that the Republicans do nothing of the sort. They're insisting that Obama and the Democrats start over--that they scrap the current plan and begin negotiations new.

Not only would that be bad policy; that would be bad politics. Both the president and his allies, I think, know that. That means it will be up to the Democrats--and the Democrats alone--to decide whether reform lives or dies.

The dynamics are pretty familiar if you read this blog or follow politics closely. On paper, just two things must happen for reform to succeed: The House must pass the Senate bill. In addition, the House and Senate must both pass a series of amendments through the budget reconciliation process, in which a majority of Senators, rather than super-majority of 60, is sufficient for enactment.

Obama wants this. House Speaker Nancy Pelosi wants this. Senate Majority Leader Harry Reid wants this. (And, yes, liberal policy wonks like me want this.)

But do the rest of the Democrats in Congress want this? The House, by all accounts, is the chamber that worries reformers the most. Centrists and freshmen are nervous about voting for a bill, given the latest poll numbers and rebuke to Democrats in Massachusetts last month. Liberals are less than thrilled about voting for a bill they deem to conservative.

The proposal Obama unveils on Monday is supposed to lay out a compromise that a majority in the House, as well as a majority in the Senate, find acceptable. Smart money says it will look a lot like what the leadership of the two chambers had negotiated right before Scott Brown's Massachusetts win changed the political situation. Apparently unresolved, still, is the question of which House votes first. And that's no small thing.

But the bigger question, really, is the broader one: Will Democrats, particularly in the House, get past their fear and vote for the bill? Really that's what the summit is all about--convincing nervous Democrats that the Republicans really aren't interested in compromise and that health care reform, despite the poll numbers, is still a good idea. (Hopefully somebody will mention to nervous Democrats the finding, consistent across polls, that the individual elements of reform remain extremely popular, even if the package as a whole isn't.)

Obama has risen to the occasion before--in his September address to Congress and his recent State of the Union Address. Both times, the consensus in Washington was that reform was dead. Both times, Obama proved that consensus wrong. This week the president needs to pull off that feat again. Or else, finally, reform may really be dead.