It is hard to predict how this translates to seat gain/loss next year. 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% toward Democrats, and 22 out of 24 points were in the gray zone. That would be more like a 35 to 40-seat gain for Democrats. An analyst would have to be crazy to predict that! However, it seems like mandatory information for a campaign strategist.
I’d like to see a Democratic SuperPAC spend a few million bucks on simple, cookie-cutter, 30 second ads in 30-40 districts with one message: your Representative voted to shut down the government. Get that message cemented in voters’ heads a year before their Rep has a chance to mount a well-financed excuse-making campaign, and you’re one step closer to a turnover.