The hard part is over. Senate Majority Leader Harry Reid kept his caucus aligned all the way to the final vote. He could have afforded to lose several liberal or conservative members, upset about the concessions they've had to make over the last several weeks, but none of them defected.
Now he'll need them to stay united for several more weeks.
According to Sen. Max Baucus (D-MT), Senate health care principals (including himself) and their counterparts in the House will begin working with Democratic leaders and White House officials next week to marry the two chambers' bills. During that process, they'll have to be mindful of just how fragile the coalition in the Senate is, and will likely make no dramatic changes to the legislation that passed this morning.
That means the House will face a vote on a final bill that's likely to be less progressive in a number of ways than the package they passed in November. Speaker Nancy Pelosi is already fielding defection threats from a number of high-profile progressives in her caucus. And given that the first bill passed by an extremely slim margin, for almost every "yes" in her caucus who becomes a "no," she'll have to find a "no" vote, and turn it into a "yes."
That's a precarious balance, and we'll be tracking the Democrats as they try to strike it.