So let me make a prediction. If Scott Brown wins the Massachusetts special election (which, while possible, still isn't very likely), health care reform will not pass. I say this not because Senator Brown would vote against cloture on it--he's promised to, but if the Democrats have anything to say about it, the bill will be voted on by the Senate before he gets there. But, if Brown wins in very liberal Massachusetts, I predict that Democratic Senators and Representatives will panic. If the bill is so unpopular that Massachusetts elects a Republican to the Kennedy Senate seat just to stop it, Democrats will desert the bill in droves. It won't have the votes to get cloture in the Senate. It won't even get a majority in the House. The same could happen even if Brown loses, depending on how close it is.
This vote is largely seen as a referendum on the health care bill, and a Brown win will be seen as a popular, and perhaps more importantly, election-deciding, rejection of it.