How Many Filibusters?

Josh Marshall gets a useful reminder in an email from the Hill that there are multiple possible filibusters on any bill, something that I've been talking about. Here's list from Josh's correspondent:

1. Cloture vote cutting off debate on the motion to proceed to the health care bill (60 votes);

2. Motion to proceed to the bill (50 votes, may be waived if we get cloture);

3. Amendments to modify the public option piece, e.g. to a trigger (likely requiring 60 votes);

4. Cloture vote to end debate on the bill and move to final passage (60 votes); and

5. Final passage of the bill (50 votes).

Joe Lieberman said today, as he has said in the past, that he is planning to vote with the Democrats to get the bill to the floor (for cloture on the motion to proceed) but not on cloture to move the bill to final passage.

Now, here's the question I have. TPM's emailer says that it would probably require 60 votes to weaken the bill by floor amendment. That's also what Ezra Klein said two weeks ago (by the way, it's in an excellent post that I should have cited against the incorrect idea that the public option looked dead at that point; Ezra was on the money with his understanding of where things actually were). I'm not certain, but I think that's wrong. Think about it: the bill is on the floor. Olympia Snowe offers an amendment to replace an opt-out public option with a trigger. Then what happens? If Democrats have the votes, they take a vote, opt-out wins, end of story. What if, however the Democrats only have 49 votes? They can filibuster the amendment...but that doesn't actually get them anything, because Republicans will be glad to let that particular filibuster go on forever. So Democrats would have the choice between keeping the filibuster going (and never getting to finish the bill) and allowing a vote. Of course, Snowe could choose to withdraw the amendment, but I'm not sure I can see why she would do that.

I do think that the Dems probably have the votes to defeat the trigger, but I think it's going to take 50, not 41.