Nate Silver examines today's NPR poll of swing seats such as Arizona's Congressional District 8:
Broadly speaking, this poll is consistent with the impression I have had of the House picture for almost a year now, which is that the over/under on the number of net Democratic losses is about 40 seats (i.e. they have about even odds of losing the House), with a 90 percent confidence interval of about +/- 20 seats. I also suspect that the race characterizations issued by Cook, etc., are about half a grade too optimistic for Democrats on average, e.g., a "toss-up" seat should be thought of as somewhere between toss-up and lean Republican, and a lean Democrat seat should be thought of as somewhere between lean Democrat and toss-up. But I'm looking forward to completing work on our House forecasting model so that we can be more exacting about this.