If Brown wins, I don't think it makes sense to continue the negotiations or trying to pass a bill through the senate prior to seating Brown. The House simply needs to pass the senate bill without revisions and await changes that will be passed in a separate bill that can be pushed through reconciliation (the content of a particular piece of legislation is critical to determining whether the rules allow it to go through reconciliation). Letting the bill die now would be stupid, frankly suicidal in political terms and good evidence that the Democrats just aren't prepared to govern the country.
For the House liberals, it was clear that only very limited revisions were going to be gained in the House-Senate negotiations. It's one thing if someone wasn't going to vote for the final bill at all. But if they were, the differences between the senate bill and whatever the negotiation was going to produce simply were not going to be big enough -- not remotely -- to justify voting against it.
For the conservative Dems, if they already voted for the more liberal House bill, it won't help them a wink to refuse to vote for the senate bill now -- whether that means casting a no vote or just preventing it from coming up for a vote at all. This should be obvious to anyone who knows how 30 second TV ads work (or frankly, even how very reasonable political argument works). And the lesson of 1994 is clear: the folks who killed health care in 1994 didn't gain any benefit from it. They were the ones who got slaughtered in November.
Let me hazard a prediction. If the Dems push through this bill now, bank the accomplish and move on to selling it and working the jobs agenda, it'll be a bad but not terrible November. If they all run to ground after a Brown victory, it's really all bets are off. Why? Because this is about meta-politics. There are all sorts of reasons for the troubles the Dems are now having. They're overwhelmingly linked to the catastrophically bad economy -- whether that's because of 10% unemployment, the spending that has been required to keep the economy from slipping into a Depression, the bailouts of the banks etc. But the key reason, the ones the Dems have some control over, is their ability to act and deliver on an agenda.
Not one to satisfy the base or to calm swing-voters. Doing either would have pros and cons. But acting. Showing voters that you're actually able to execute. This is what is hurting Dems across the board. Ideological voters think in terms of their policy wishes. But not all voters are like that. And not just 'low information voters'. Voters respond to the ability to act, to get results. That may sound trivial or shallow but it's not. It's both logical and goes to the heart of all of our experience of human nature. Democrats need to show that they can act and have some confidence in what they're doing. So pass the bill and move on.