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When The (Gerrymandered) Levee Breaks: North Carolina and Michigan

November 3rd, 2018, 1:01am by Sam Wang


Back in 2013, I wrote about the hidden vulnerability when a party engineers winning districts for itself. This idea is in full force for 2018.

Gerrymandered wins may swing back hard, because they often have a mix of Democratic, Republican, and most important, independent (and maybe swingable) voters. This would explain some surprisingly close races in North Carolina and Michigan.

To quantify this, let’s look at GOP-held districts in 3 gerrymandered states: N.C. (CD 2/7/9/13), Michigan (2/6/7/8/11), & Ohio (1/12/16) in which polls are available. In every one of these 12 districts, Trump received more votes than Clinton by an average margin of 11.6%.

The incumbents ran well ahead of Trump, winning their last election in 2016 by an average of +20.7%. But now, those same districts show an average Republican lead of only 2.8% – an 18-point swing toward Democrats. That is twice as large as the swing in national polls, which has gone about 9 points toward Democrats.

Here’s a comparison for all districts, with the swing calculated between the 2016 House margin and current 2018 polls:

2016 margin Trump-Clinton Oct. 2018 polls Swing toward D’s
NC-07 R+22.0% R+17.7% D+4% 26 points
MI-11 R+12.7% R+4.4% D+1% 14 points
NC-02 R+13.4% R+9.6% D+1% 14 points
NC-09 R+16.6% R+11.6% Tie 17 points
OH-12 R+36.7% R+11.3% R+1% 36 points
MI-08 R+16.8% R+6.7% R+3% 14 points
NC-13 R+12.2% R+9.4% R+3% 9 points
MI-06 R+22.2% R+8.4% R+4% 18 points
MI-07 R+14.9% R+19.0% R+4% 11 points
MI-02 R+30.3% R+17.6% R+6% 23 points
OH-01 R+19.2% R+6.6% R+9% 10 points
OH-16 R+30.8% R+16.7% R+9% 22 points

Democrats lead in three of these districts – NC-02, NC-07, and MI-11 – and are tied in NC-09.

So the levee is at risk of overtopping slightly in North Carolina. This is a state where a racial gerrymander was struck down and replaced with a map that was still partisan – but did not use race in the same way. The resulting gerrymander gave Republicans a slightly narrower margin of safety. Think of it as removing the top layer of sandbags from the levee.

In Ohio and Michigan, the partisan maps seem to be holding up better. Still, in 9 out of 12 districts in these three states, the polling margin is within 5 points in either direction. That’s cutting it pretty close.

Does this mean that gerrymandering doesn’t matter? Not at all. These districts were safe for their incumbents in 2012, 2014, and 2016. 2018 is quite a large swing by historical standards – larger than the swing from George W. Bush’s popular margin in 2004 to Barack Obama’s in 2008. Of course there’s some point at which a gerrymander fails. There always is. That doesn’t change the fact that these districts were engineered to be uncompetitive under a wide range of normal political conditions.

Postscript: Also note that legal actions have been chipping away at gerrymanders for several years now. Dave Daley documents the slow, steady progress.

Tags: 2018 Election · House

One Comment so far ↓

  • ArcticStones

    These districts were gerrymandered for what the Republican Party once was. But will that gerrymandering be successful for candidates from the party it has morphed into?

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