I think the Democratic Congress made a mistake in mostly giving in to Bush on Iraq war funding. I also think John Edwards is wrong, although less so, in saying the Democrats should've kept sending Bush still more bills with timetables in them for him to veto.
Instead, the Democrats should've done what they had suggested earlier, sending bills with short-term funding of two or three months, and take Bush on in the constitutional crisis he threatened. I think this is similar to what Edwards would've done, except that it would leave the Democrats in a stronger position.
Bush said if he got a short-term funding bill he would veto that, too. Fine. The Democrats can say "we want a timetable to get out, but Bush won't allow it and we don't have the votes to override, so instead we're willing to fund the effort for a short time period and see what happens afterwards. We're simply not going to fund an open-ended war." Bush can try and argue that Democrats aren't funding the troops, but each time the Democrats can just send him a new short-term funding bill. I expect he'll veto it each time, and the military will come closer to a point, some time in mid-summer, when it won't have funding for the war.
Then Bush has a choice, and the Democrats a response to either choice he takes. Bush can obey the law, and begin a precipitous withdrawal, blaming Democrats for the inevitable chaos that he says will follow. Immediately, the Democrats respond by passing a new funding bill dedicating money only to an orderly withdrawal from Iraq over the next four to six months, while allowing to stay (and fund) behind whatever non-combat forces that the Democrats choose to allow. I have trouble believing that Bush would veto this bill as well, leaving M1 tanks and Bradley fighting vehicles in Iraq - and if he did, it's the one veto that would get overridden.
Or Bush will take the unitary executive theory to its extreme, saying as long as Congress has not rescinded the 2002 Iraq military force authorizations, he doesn't need Congressional approval and can spend money without it. While there is some US Civil War legal authority for very limited spending in this situation for a limited time, no precedent would justify an open-ended war.
So then Bush provokes a constitutional crisis. Democrats respond by suing to force him to stop, and the courts either refuse to rule on the issue as a political question or fail to resolve the issue before January 2009. This isn't a Bush victory, unless you call unmasking a dictatorship a victory for the dictator. Instead the war will be seen as all that much more illegal, Bush will be that much more isolated, and Republican congressmen and Republican presidential candidates would have to announce whether they support the interpretation of the president as a dictator.
I think it would have brought us closer to ending the war without having to wait for a Democratic president, without the Democrats getting blamed.
I'll acknowledge that the actual Democratic approach has created benchmarks. Failing to meet these benchmarks will have no real repercussions, but the Democrats will use the failure to call again for a withdrawal. Still, that's not enough to give Bush another year of authorization for catastrophic failure.