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Expert Brief

What It Takes to Win: How Gerrymandering Will Skew the 2018 Election

The results won’t reflect what voters want. That underlines the urgent need for fair maps.

Published: October 18, 2018

The stakes for this year’s midterms could hardly be higher. And yet, the results almost certainly won’t come close to accurately reflecting the will of voters.

According to most analyses, Democrats will need to win the nationwide congressional vote by a substantial margin just to win a bare majority of House seats. That’s in large part because of extreme Republican gerrymanders in several big states. The Brennan Center’s interactive map, created with our partners at Development Seed, shows the effect of those gerrymanders on election results.

Fortunately, there’s a solution: reforming the redistricting process to strengthen rules on fairness, or even taking map-drawing out of the hands of partisan lawmakers altogether. In fact, initiatives to do just that are on the ballot in several states this fall. By using fair maps, we can ensure that election results reflect what voters actually want.

How to Use the Map:

Districts across the country tend to shift uniformly in response to changes in the national vote. So by adjusting the bar that controls the parties’ national vote share, you can see how their projected share of seats increases or decreases — including the fact that if both parties win 50 percent of the vote, Republicans will still wind up with many more seats. You can also look at individual districts to see which seats change hands as the national vote changes, and to see assessments by two leading election prognosticators, 538 and Larry Sabato. (Note: The 538 number is their estimate of Democrats’ percentage chances of winning the seat, not Democrats’ expected vote share.)

To be clear, the actual national vote percentage needed for Democrats to win a majority may be somewhat lower than the map suggests, especially in a wave year. That’s because of district-specific factors like retirements, scandals, or exceptionally weak or strong fundraising. While some election analysts take those factors into account in formulating their estimates, our map focuses solely on the raw effects of gerrymandering — showing how rigged maps put one side in a hole from the get-go and thwart the will of voters.