Under the U.S. Constitution, every ten years, the 435 seats of the House of Representatives are to be reapportioned between the 50 states based on the results of a census. Over the past year, following the 2020 census, every state (apart from those only allocated a single seat) have been deciding how to divide themselves into Congressional districts. These districts will be in place for this year’s midterm elections, and most of them will be in place until the 2030 midterms.
Every state has its own process for drawing these district boundaries. Some states set up non-partisan commissions that aim to draw the lines as fairly as possible. In other states, politicians in the majority party take responsibility for drawing the lines, some scarcely concealing the fact that their aim is to give their party an unfair advantage. In a few cases, the courts have had to draw the boundaries after the legislature failed to produce a map that was deemed to be consistent with their respective state constitutions.
As maps have been enacted into law, I’ve been attempting to unscramble the votes cast in 2020 and place them into their new districts, to see how the old districts and the new districts compare.
Winning in 2022
At the 2020 election, Democrats managed to hold onto their majority in the House of Representatives. But their majority was significantly reduced, taking only 222 seats against the Republicans’ 213.
These new districts have notionally given the Democrats four more seats, meaning that their start position for these midterms becomes 226 against the Republicans’ 209. However, that only tells part of the story. The other part of the story is how easy would it be for the Republicans to take the majority for themselves? The answer: actually, slightly easier.
The way I like to measure how easy it is for the minority party to win control of the House is to look at the tipping point district; sort the districts from most Democratic to most Republican and look at the 218th seat on the list. If the swing needed to take the tipping point district is replicated, on average at least, across all 435 districts, then that should be enough for control of the House to switch parties.
On this measure, even before redistricting, the swing that Republicans needed to take the House wasn’t very big at all. After redistricting, it’s become even smaller.
One key difference between the old and new districts is the number of seats Democrats won in a small margin. In the 2020 election, the seat that Democrats won by the smallest percentage margin was on a margin of 1.22%. When adjusted for the new boundaries, there are six districts that the Democrats notionally won on smaller margins.
It’s worth noting that Democrats had an overall 3.1% margin of victory in the popular vote in 2020; the fact that the tipping point district has a smaller margin indicates that the Democrats will continue to need a higher vote share than Republicans to win control of the House, just as they have since the last redistricting a decade ago.
The Extent of Gerrymandering
Of the 44 states that have more than one district, 35 of these states’ Congressional boundaries are drawn by politicians in the state legislatures. In many of these states, especially in those where a single party controls both chambers of the legislature and the Governor’s mansion, politicians will try to draw the lines in a way that gives their party an unfair advantage.
The way that I measure how unfair a state’s districts are is by comparing the margin of victory in the statewide popular vote, with the margin of victory in the tipping point district in that state (or, where a state has an even number of districts, the average between the two tipping points). It is, of course, possible for very partisan states to draw their lines fairly (Oklahoma and California being two big examples of this). But many states decided not to.
Of those states that used an independent commission or a political commission to draw their lines, most of these differences were well under 1%; the largest difference, in Colorado, was 3.8%. Contrast that to the worst state of all, Missouri, where Democrats would need to get a 17.7% higher share of the vote than Republicans to get a majority of seats in the state.
In total, eight states have a difference of more than 10%, putting them on the Gerrymandering Wall of Shame.
The U.S. Midterm Elections will be held on Tuesday 8 November 2022.
