Just finished reading Jeffrey Feldman's diary on negotiating and the Iraq funding - read it, read it now, this diary will still be here. The basic point was "Why are the Democrats still at the table?" The question is cogent and fundamentally puzzling. May I offer an answer?
The 2008 Presidential election is coming. That one single statement and all the consultants grouped around it offer the glimmer of an explanation. Look at the voting on the prior Iraq war measures - presidential candidates waiting until after the decision was made before casting ballots. The "follow from the front" strategy - figure out where everyone else is going and get in front of the parade.
In that context, the "negotiation" strategy allows the senatorial candidates to have their "strong on terror" cake and eat their "we had to follow the leadership" too. It's not pretty, it's not productive - but it is politics.
That said, what can be done?
First, the campaigns have to pressure leadership in the senate. DKos is doing this but I would not be surprised at all to see senior staff at some campaigns quietly supporting Reid - after all, it provides both sides of the coin at someone else's expense.
Two, it has to be perfectly clear - is the concern here about governance or power? The neo-cons have shown the leadership in power over governance for the last seven years (or more). It is a lesson Democrats are learning - so is that lesson more important than the correct decision on Iraq?
Three, is the presidency worth it? Let's just suppose, hypothetically, that taking Iraq funding to the brink and forcing substantial and viable negotiations over the withdrawal of troops is something that would severely endanger the election of a Democrat as President in 2008? Which option would you choose? I know, I know, taking the right stand would assure their election - but that ain't what they are hearing in their strategy sessions. So, are you feeling lucky, are you?
Only then can the appropriate pressure be brought to bear. Only if enough supporters and donors are willing to say - "Your position on this issue is a bright line decision - if you are with me, I support you; if you don't, I go elsewhere." Only then do you have the leverage you need to negotiate their actions.
otherwise, you have no best alternative. If you will support your candidate regardless, then give up now.