Cook cites some examples of national polling data, to show that the Democrats are no longer untouchable. President Obama's approval rating is now consistently hovering just above 50%. There is also heavy disapproval of Congress, with 70% disapproval among the key independent voters in the latest Gallup poll. It should be noted that there isn't anything in the way of race-specific data, which doesn't really exist and wouldn't be of much use at this early point in the cycle.
The analysis later adds: "That all of this is happening against a backdrop of an economy that appears to be rebounding and a resurgent stock market underscores how much the President's and his party's legislative agenda have contributed to these poor poll numbers."
It really is interesting to consider what has happened here. Democrats have the White House, 60 Senate seats and 257 House seats -- but they have managed to lose control of the debate and a sense of party cohesion.
Taking Cook's analysis at face value, a loss of 20 seats wouldn't be too bad. It would simply take Democrats back to where their majority was before the 2008 election. And some kind of loss was bound to happen, considering that Dems won nearly everything they could in two successive wave elections in 2006 and 2008. The only real question is whether the losses will be a minimal erosion of Democrats from the political landscape, or a larger-scale mudslide.
But the trend isn't encouraging, either. It would take a loss of 40 seats to actually flip control of the House back to the Republicans -- and 20 is closer to that than six or twelve are. A lot can happen in the next year, and any of these trends can flip around again. But this summer definitely seems to have thrown the Dems off balance.