PPP surveyed 24 congressional districts currently held by Republicans. They asked voters to choose between their current representative and a generic Democrat. (Details are at http://front.moveon.org/wp-content/uploads/2013/10/PPP_House_Survey.pdf). In a chart, they graphed the margins they got, plotted against last November’s election result. The swing was toward Democrats for 23 races and toward the Republican for one race. The key piece of information is the gray zone. If more than half the points are in that gray zone, then that predicts a swing of >6 percent and a Democratic takeover. Currently, 17 out of 24 points are in the gray zone.
Individually, the district-by-district swing is quite variable, +4 percent to -23 percent (where + indicates a swing toward Republicans). But the average is clear, -10.9+/-1.5 percent (mean+/-SEM). That predicts a national popular-vote margin of D+12.0 percent.
Since the election is over a year away, it is hard to predict how this will translate to future seat gain/loss. If the election were held today, Democrats would pick up around 30 seats, giving them control of the chamber. I do not expect this to happen. Many things will happen in the coming 12 months, and the current crisis might be a distant memory. But at this point I do expect Democrats to pick up seats next year, an exception to the midterm rule.
Note that in these calculations I did not even include the worst of the news for Republicans. In a followup series of questions, PPP then told respondents that their representative voted for the shutdown. At that point, the average swing moved a further 3.1 percent toward Democrats, and 22 out of 24 points were in the gray zone. That would be more like a 50-seat gain for Democrats — equivalent to a wave election.
Of course, the big question is how the current snapshot, a probable House turnover to the Democrats, will evolve in the coming 12 months. At the moment we are in territory that resembles 1995, a shutdown with blame going largely to congressional Republicans. If the government is funded with a continuing resolution (CR), then opinion could easily swing back and the GOP could hold on to the House. But what if the government hits the debt ceiling? In such an extreme circumstance, which has been called the domestic equivalent of the Cuban Missile Crisis, the outcome I have calculated here becomes quite a plausible scenario.
At this point, an analyst would have to be crazy to predict that that will happen. However, it seems like mandatory information for a Democratic campaign strategist — or any Republican incumbent who won by less than 20 points in 2012.