Crass politics, now:
a.) If Sen. Ben Nelson supports it, that means the rest of the Senate Democratic moderates probably will support it, too.Looks to me like the politics say that this will be the compromise. Or, of course, the whole effort could fall apart.
b.) If Sen. Olympia Snowe also supports it, that probably gets Democrats to 60.
c.) If Nelson and Snowe support it, it seems reasonable to believe that some House Blue Dogs will also support it, for the same reasons.
d.) Last but not least, if Rep. Anthony Weiner says House liberals probably will accept it, they probably will.