Via LG&M, Kevin Drum explains:
If Republicans really did put up a united front and filibuster the legislation, the Democratic leadership would just turn around and consider the bill under budget reconciliation rules, which require only a majority vote to pass. Sure, they've already said they'd prefer not to do that, but if they have to they will. And since the bill is all about short-term spending, it would obviously qualify under reconciliation rules.
So all the public handwringing seems like standard DC negotiating kabuki to me, not a genuine effort to kill the bill. If Republicans filibuster, the public will view them as bitter obstructionists and the bill will pass anyway. It's hard to see what's in it for them to go down this road.