US House Redistricting: Iowa

[Frodo]

Here’s the 538 GOP gerrymander:

https://davesredistricting.org/join/60cda9dc-5f6e-491b-a0dd-232b9563018c

It looks like they could make a Dem vote sink in east IA to shore up the other three districts, plus crack Des Moines between IA-3 and IA-4.

Obviously it’s outdated and I don’t know what maps the new population would make.

You can't split counties in Iowa by law (unless necessary for population equality, but in Iowa it's not because of the plethora of tiny counties).

Didn’t know that. Would it be possible to make a map with R-leaning districts?

They’d probably combine Polk with Story for a D vote sink. Then the leftovers of IA-3 can become part of the new IA-4 and the eastern remnants of the old IA-4 can become part of IA-1.

Also, is it possible to put Linn, Johnson, and Scott in one district so shore up IA-1 for the GOP?

Basically the way redistricting works in Iowa is that there is an extremely strict formula for how districts can be shaped, and counties can't be split. So they run a program that spits out a bunch of legally acceptable maps, which are created totally algorithmically, and then the legislature picks from among those options. The legislature can also ignore the program's choices and create their own, but they still have to follow the extremely strict rules about district shape (in particular, I believe the rule is something like that districts must all have a low ratio of their north-south axis to their east-west axis, but more mathematically determined than that), so there would in practice be no more than tiny deviations from what the program spits out (usually just switching one <2,000 person county for another).

This in practice means that gerrymandering is not really possible in Iowa, and you sort of get what you get by the population distribution. So you can't really actively try to favor one party over another. The Democrats did get pretty lucky in the 2010 map, especially given later trends in the state, but it was really just luck. Also, if you read earlier in the thread, it was considered a favorable map for the Republicans at the time.

So Iowa Republicans are better off focusing on redrawing the legislature.  

[Frodo]

Put together a State Senate map:



https://davesredistricting.org/join/3292b655-5664-42a6-9abd-f9433c58b7dd

Seat composition:
2016: 34 Trump — 16 Clinton
2018: 31 Reynolds — 19 Hubbell

State House map:



https://davesredistricting.org/join/777a517a-251c-4e74-a547-5cb37e6b7f14

Seat composition:
2016: 66 Trump — 34 Clinton
2018: 57 Reynolds — 43 Hubbell

Can you get these maps color-coded for partisan purposes?  I have no doubt I will see a Republican sea of red (or Atlas blue) interspersed with a few tiny Democratic islands, but still.  

[Frodo]

Can you get these maps color-coded for partisan purposes?  I have no doubt I will see a Republican sea of red (or Atlas blue) interspersed with a few tiny Democratic islands, but still.  

Sure - here you go. Data from the 2016 presidential election is used for both maps.

House:



Senate:

Thanks!

[Frodo]

Iowa Senate, House approve second set of proposed redistricting maps
The map will go to Governor Reynolds for her signature



The congressional map is not the only map that was approved by the legislature:

[Frodo]

I know Iowa Republicans are happy as clams with these maps, even more so knowing they didn't have to do much if any gerrymandering -the natural concentration of Democrats into cities and other population centers did that for them, ensuring that Republicans will hold on to the legislature for at least the remainder of the decade.