Please note. Throughout this memo partisan baselines for each district are calculated as the average of the 2020 presidential, 2018 gubernatorial, and 2016 presidential elections. Seats “won” by either party are calculated by applying a uniform swing to this partisan baseline. This does not take into account incumbency effects.

Partisan lean of proposed plans

I define a “competitive” seat as one with a partisan baseline of 5 points or less. In other words, neither party typically receives more than 52.5% of the 2-party vote. By this definition, the current maps contain 1 competitive Congressional seat. The WI Legislature’s plan would leave this unchanged. The People’s Map Commission would create 2 competetive seats.

Partisan lean of seats in proposed maps
Democratic Republican
0-5 D Safe D Safe R 0-5 R 5-10 R
People's Map Commission 2 2 4 0 0
WI Legislature 0 2 4 1 1
WI 2011 0 2 4 1 1

Seats by swing

This graph shows the number of Congressional seats won by Democrats depending on the statewide vote swing. By far the best map for Democrats is that proposed by the People’s Map Commission. Under this plan, Democrats could expect to win half the seats in a statewide tie. They would need to win the state by about 13.2 points (i.e. 56.6% of the 2-party vote) in order carry 5 seats, or a majority of the congressional delegation..

The plan proposed by the Wisconsin Legislature is substantially worse than even the existing plan. If that plan were enacted, Democrats would likely win 2 seats in a statewide tie. They would need to win the state by 15.5 points in order to carry a majority of seats (i.e. 57.75%).

 

Democratic electoral performance across selected district plans
seats in statewide tie minimum swing for majority
People's Map Commission 4 13.2
WI 2011 2 16.3
WI Legislature 2 15.5

 

District changes

Consequences for incumbents

Please note. All these calculations are based on the most recent address I could find for each incumbents. Some incumbents may have moved, making these results outdated.

As the map suggests, the People’s Map Commission makes the most dramatic changes to the existing map, whereas the WI Legislature’s proposal mostly makes small tweaks. Over ninety-three percent of the population would remain represented by their old incumbent under the Legislature’s map. Around 63.5% would be represented by the same incumbent under the Commission’s proposal.

 

Total population with the same incumbent
population
total voting age
People's Map Commission 63.5% 63.3%
WI Legislature 93.5% 93.6%

 

As with the other maps, the WI Legislature’s plan appears to priortize incumbent retention. Based on the most recent addresses available, all 8 curent representatives would find themselves in a district with no other incumbents.

By contrast, the People’s Map Commission would place half the incumbents in their own districts and the other half in districts with multiple incumbents. Two districts would be created without a resident incumbent.

 

Incumbent protection statistics by plan
Districts with this # of incumbents incumbents in multiple incumbent districts
0 1 2 3
WI Legislature 0 8 0 0 0
People's Map Commission 2 4 2 0 4

 

The graphs below show how each Congressional district would change under each plan, regardless of whether or not the current incumbent would reside there.

For each district, the arrow extends from the partisan baseline of the current boundaries to the partisan baseline of the proposed new district if the plan in question was adopted.

WI Legislature’s Plan

People’s Map Commission Plan

Appendix