Check out this piece from the Washington Post:
For Democratic congressional leaders, the dog days of August are looking anything but quiet. Having failed twice to crack GOP opposition and force a major change in war policy, Democrats risk further alienating their restive supporters if the September showdown again ends in stalemate.
This is why the best strategy for Congressional Democrats may be to cave. If they can end the fight over Iraq quickly, it may expose them to less abuse from their base, and allow them to move on to issues that unite Democrats and divide Republicans