"I'm worse than Hitler?" - Jay Sherman
"Not worse, just less warm and cuddly. Jay, test groups like this determine what you watch on TV, what kind of car you drive, even who runs this country." - Duke Phillips
Back in July, I took a detailed look at the House map and concluded that the Democrats had only the longest of long shots to retake the House. Three months and one Donald Trump poll implosion later, and the odds have improved enough that it actually makes sense to take another look. So, how hopeful should we be for a Blue House majority?
First, there are three (3) big unknowns to overcome. 1) House polling is expensive, and doesn't lend itself well to clickbait articles, so there is very little publicly available polling on individual House races. The main tool we have is the "generic ballot" question, which is usually tacked onto other polls and used as a stand-in for the House race overall. This means we simply don't have the data to make a prediction on a district-by-district basis, so we have to use the generic number as a stand-in.
That brings us to problem number 2), there isn't a 1:1 correlation between the overall House vote and the number of seats each party wins. Because each district is its own self contained contest, an increase of 1% in the Democratic vote nationwide might translate into anywhere from zero extra seats to five or more depending on where those votes come from. As a further wrinkle, Republican controlled seats tend to come from much whiter districts (duh), so the shift in the white vote will affect Democratic House outcomes a lot more than a surge in Latino voting or 2008/2012 turnout levels among black voters.
Muddling matters even further is number 3): this will be the first Presidential election run after the grotesque Shelby County decision. Since 2013, a slew of Republican controlled states have enacted all manner of voter suppression laws, and many of them are actively fighting and ignoring court orders to drop them as we speak. We can't know how many, but we can be damn sure that thousands, perhaps even hundreds of thousands, of Democratic votes will be "missing" because of reductions in early voting, restrictive ID laws, and similar fiendery.
TL;DR for the above is that we're trying to use a general number to account for hundreds of distinct contests, each of which has its own complications based on local politics, voting restrictions, and gerrymandering. So the best we can do here is make some educated guesses.
The baseline we're going to start with is the 2012 election, which saw the good guys win a 1.2% overall victory in terms of House ballots (a margin of 1.4 million votes). Despite that, the resulting House was a Republican blowout of 234-201 in terms of seats. That's the hole we have to climb out of. Our own Stephen Wolf puts the likely margin needed at 7-8 points which accords with what Harry Enten (now of 538) thinks.
The generic ballot polling in 2012, especially once it got into October (when polling accuracy tends to get much better) was pretty close to the actual outcome, with a slight Republican lean. The polls from October forward ranged from +3 Republican to +2 Democratic, with Real Clear Politics placing their final weighted average at +0.2 Republican, which was 1.4% off from the actual outcome.
The current RCP average is +5.0 Democratic, and the polls that produced it range from +3 to +10. That's probably not going to be enough, but if the Democrats out-perform their polls by the same 1.4% margin they did in 2012, that would put the margin at +6.4 Democratic, which is still short of 7, but close enough that immeasurable factors could flip the chamber. Plus there was a Politico/Morning Consult poll this morning that isn't in the RCP average yet. It was +7 Democratic.
Given all the fudge factors above, I'm not going to assign a probability to whether or not the Democrats can take the House. Any number I give would be pulled straight out of my ass. But what we can say is that if the polls hold roughly where they are, the Democrats have a puncher's chance, which is a hell of a lot better than things looked over the summer.