> There are many mathematical ways to detect “unreasonable” gerrymandering.
But what does that mean?
Suppose you have a state with four districts and the state as a whole goes for one party by 60-40. You could then draw four districts that are all 60-40 and that party gets every district in the state. Is that unreasonable? It's what you would expect to happen if the state is fairly uniform and you draw the lines completely at random or using a method that otherwise doesn't consider how each neighborhood is expected to vote whatsoever.
Or you could draw two districts that are 20-80 and two more that are 100-0, and then each party gets half of the state, which is the number of districts you would expect based on a 60-40 split because 60-40 is closer to 50-50 than it is to 75-25. Is that unreasonable?
Or you could try to minimize the number of safe seats where representatives don't have to be responsive to voters because they can't lose. The majority party would still have one, but then the other three districts would be around 50-50, with the possible result that the minority party could get 3 of 4 seats. Is that unreasonable?
There is no "correct" way to do it. Each party is going to want the one where they get more seats.
> As for the racism involved, you’d have to be intentionally ignoring all history to pretend that this is just because minority populations prefer Democrats, especially given that the players involved on the Republican side are pretty explicit in their private communications that manage to leak that it’s about race and protecting the white vote.
You're linking to things that don't actually say this. When drawing the districts they have maps where the race of the constituents is known. Certainly so do Democrats. But for this to be their actual motive -- and for it to have any consequence over their stated motive -- they would have to be choosing it instead of some alternative map which is better for them in terms of seats but worse in terms of something like "white representation", e.g. they prefer a district map that would result in two white Democrats over one black Democrat and the other seat going to themselves. Whereas drawing a map that maximizes the number of their own seats over any other consideration is an obvious demonstration of what they really care about.