The Supreme Court was right that there is nothing in the constitution from preventing political parties from giving themselves an advantage with voting districts. It was a failed strategy.
File the same case showing how it disproportionately impacts voters for certain races and the outcome is wholly different.
The argument is that it isn't enough to have the right to vote, but you also have to have the right to vote meaningfully. Getting packed into a district takes away that right. I think it's a strong argument, and would have won with a different Supreme Court. Kennedy actually was receptive to it, but had issues with how to weight it.
Functionally, if you can argue that you are allow to pack voters based on politics, it is a back door to eliminating minority voting power as well.