It is also illegal on the grounds of being a black pack where race rather than partisanship drew the lines.
Yes, although bear in mind that the facts were unusual in the NC case. The Pubs thought they had to gerrymander to get over 50% black, so it was the blacks that they were going after rather than Dems. That was because they guessed wrong as to what the law was.
Now nobody expressly goes after blacks, in a gerrymander, or admits it, once a CD is black performing. Rather it is all about going after Dems. It is akin to a tyrancal Goldilocks rule. As long as a CD is deemed "compact," you go after blacks until a CD is black performing. but if you then go past that and gerrymander further, to get the black percentage up more, then it is also illegal. It must be just right or else. So, that is why lines are drawn based on party preference but not race as an initial matter, and then you check to see if, where Gingles is in play, you have the requisite performing black CD's. If not, then you move the lines around until you do, but no more.
From the Pub perspective, the best practice is to start by hewing to jurisdictional lines and compactness, and if not Pub enough, get less compact and chop more to the extent necessary to get to the right level of Pubness, and then check, if Gingles is in play, as to whether you screwed the blacks out of a performing CD, and if so, revise as necessary to make it all legal.
Quite often you can get a satisfactory Pubmander just by doing step one, and have a nice pretty map. I did that with my MI Pubmander the other day. Remember?
