From one perspective, the Democrats' decision to approve a war spending bill without a timetable certainly appears so. You can tell the Dems are divided over it, and I imagine that this isn't so much political as personal. I really doubt Pelosi is playing sillybuggers on this.
That said, I do think they were up against a wall. They didn't want to be portrayed as obstinate to the point that the troops don't get needed supplies, they don't have a veto-proof majority, and they're up against a president who is clearly totally unconcerned by the 2008 election and, thus, isn't going to bend for political purposes.
(I'd said back in 2004 that this would be a problem. Now we're seeing it really hit home, now that he doesn't have Republicans running the show to roll over for him.)
It's frustrating, but I think it has more to do with term limits (which create politicians with nothing to lose, a dangerous combination) and the unfortunate reality that impeaching the man's sorry butt is impossible than any real Democratic weakness.
Edit: Again, people are missing the point that political tactics won't work on an administration with nothing to lose politically. If he's guaranteed to stay until '08, and doesn't give a crap about Republicans' chances in '08 either, then he has no reason to bend.
It's like playing chicken when the other guy is controlling the car by remote control- you can't win, because he's got nothing to lose.
The only solution is to threaten impeachment. But, well, that door's closed, isn't it?