G. Elliott Morris Profile picture
Feb 19, 2018 11 tweets 4 min read Twitter logo Read on Twitter
New #PA Congressional map is pretty much the best one Democrats could have hoped for. At least 2 pickups in neutral environment, likely ability to win 11 in current D+6 environment. Post coming
PA redraw creates map that is almost entirely drawn from scratch. Huge shifts from 2016 plan all over the place. Dems favored to win 9 seats there in almost any national environment.
(big swings mostly from renumbering, but aggregate differences are clear)
Whereas the current PA map had a mean-median difference of -7% (a bias towards the GOP), the new court-drawn map is much smaller 3% bias.
Since we’re at this point in the generic ballot where we would have predicted ~7 Dem seats in PA, the new map isn’t the enormous boon for Dems that some are making it out to be. A victory? Of course. Less bias? You bet. But a game-changing redraw? Perhaps, but maybe not.
The new map will be rolled into the 2018 forecasting model soon*. New estimates will have larger standard errors, of course, but expect a modest increase in D probability of taking back the House.

*sometime in the future, at a definite point, but unspecified, maybe indifenitely?
OK, the new PA Congressional map is (A) half as biased toward Republicans, (B) still gives them an upside over Pres performance, (C) points to Dems winning 9 seats in Nov (in current environment) (D) creates big upside in small D wave (E) REALLY MESSED UP NUMBERING. LIKE WTH GUYS
#NEW PA court map is about 2 seats nicer to the Democrats. Here are the changes between districts (old %ages matched up with their new numbers):
My original #PA map tweet was a little optimistic for Dems: 11 seats very unlikely. Instead, here’s the PA forecast under new vs old boundaries: Democrats all but guaranteed 9 seats at the outset, a huge improvement under old map, but dummymandering already had Ds getting 7.
(be careful interpreting this because we have no earthly idea what incumbents are about to do)
Been seeing takes saying new PA map is a Dem gerrymander. Nope! Still has a 3% bias toward the GOP (per mean-median test). And per my models, Democrats don’t even win a majority of PA’s seats until they win the House popular vote by 16 (SIXTEEN) points.

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More from @gelliottmorris

May 13, 2018
This is the right take (if I’m reading it correctly), but let’s talk about that article claiming the Democratic wave is receding (nymag.com/daily/intellig…). Oh boy...
Best evidence of REAL change in the wave is in actual voter behavior. If Democrats stop posting gains in special elections over time, they should worry more. Of course, they haven’t (yet?). These claims are almost all based on declining D margin in the generic ballot, which...
... is mostly an artifact of how wide you take your averages. Monthly Democratic margin in generic ballot polling has been between 7 and 9 percentage points since October of 2017. Combine with special elections, the wave looks nearly as tall as it did in March.
Read 7 tweets
Apr 25, 2018
There are TWELVE special elections tonight! One high profile election in #AZ08, a Trump +21 congressional district, and eleven (11!) in New York, where two R seats are competitive possible flips.

Coverage to follow here. <THREAD>
With results being dumped in for #NYSpecialElections, we have our first calls of the night… 3 holds for the Democrats.

NY #SD32: D hold (Clinton +88)
NY #HD74: D hold (Clinton +74)
NY #HD80: D hold (Clinton +66)
Democrats also hold NY #HD39 (uncontested) which Clinton won by 66 points in 2015. They are batting 4/11 tonight.
Read 32 tweets
Mar 14, 2018
27% in now. Unclear if Lamb can pull this off. He’s running out of votes in Allegheny
Not sure if anyone else is seeing this or my data is messed up, but pretty interesting nugget — seems like Clinton precincts are voting a little worse for Lamb than her, but turning out much more. R precincts going more for Saccone than Trump, but voting far less.
This is a story of turnout
Read 52 tweets
Mar 13, 2018
TONIGHT is the much-hyped #pa18 race between @ConorLambPA and @Saccone4PA18. Who’s going to win? Predictions and results: [THREAD]

Before 8PM rolls around, I want to cover what the data say to expect in this contest. This thread will start off running through my predictions, will cover how I’m projecting the race, and will turn into a live blog with graphics when the votes start to come in.
There are multiple ways to predict an election. Polls, geographic data, demographic data, etc are all useful. I’m going to run through what all these measurements could predict in #pa18. Spoiler: it’s a mixed bag for both Lamb and Saccone.
Read 28 tweets
Feb 19, 2018
#New PA cong. map increases D chance of winning the House majority by 4%. They only need a 6.8% generic ballot margin now (down from 7.7) to be favored.

Diff. will be closer to 10% in Nov when uncertainty from polls is ⬇️. Redraw is a very big deal.

One major reason the new PA map is such a big gain for Democrats is that it solidifies, not just tips, PA districts in Philly burbs. Also creates one additional vulnerable R district. (Easily seen in this map made by @JMilesColeman)
My forecasting model will have new PA map in the near future. This is not just a simple switch; it’s a coding redesign, restructuring of input, & drawing new geographic files. Takes a while (for me, a student).

In the meantime, just add 3-4% to the model: bit.ly/2018_house
Read 4 tweets

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