18%, down nine points since mid-July, 14 points lower than Bush’s own numbers right now, and matching the lowest approval rating they’ve had since they started polling 1974. Their disapproval rating? 76%.

What accounts for the sharp drop in the past four weeks? The public has known for months not to expect any action on Iraq until September; besides, there’s actually been some good news to report. The shamnesty debacle was over by the end of June so that would have shown up in the last poll, not this one. The Democrats caving to Bush on FISA annoyed the nutroots but I doubt it bothered the Democratic establishment enough to force an almost double-digit drop. What can explain it? Earmarks? It can’t be earmarks. Whatever it is, though, it’s bugging the left, not the right:

The nine-point drop in Congress’ job approval rating from last month to this month has come exclusively from Democrats and independents, with Democrats’ ratings dropping 11 points (from 32% to 21%) and independents’ ratings dropping 13 points (from 30% to 17%). Republicans’ 18% approval rating is unchanged from last month.

The worse their numbers get, the more pressure Reid and Pelosi will feel to dig in on Iraq next month to get them back up. The last thing the Democrats want is to have to spend money that should be going towards defeating Republicans next year on defeating primary challengers instead. Bush’s best chance to temper their recalcitrance was to make enough progress on the surge before September to swing public opinion significantly on the war, but that hasn’t happened:

Next month’s going to be a rough one.