So there is Justice Kennedy, for all that: unmoved by the facts of the case and still groping for a standard.Oh there is much more to the opinion (a lot more), but from the very fast read I have given it, this is the best summary.
For those who don't know or don't remember, Justice Kennedy was the fence sitter in the Vieth v. Jubelirer which also dealt with a partisan redistricting.
With Kennedy looking hard for a standard, this is going to be a very fluid area of the law. Look for the next case dealing with partisan redistricting to arrive at the court based on a circuit court split. The Court is going to want some better facts to deal with, and I tend to agree.
I however, do believe a standard can be found. I think most people are looking for a voting rights or a representational rights standard that will look at the voters as individuals. I think a better standard might be to look at process. Namely, the voters may have a better chance of winning if we are looking for a standard based on a due process or procedure right, rather than a voting right. Thus, if the state were to establish a written procedure, whether followed by the state legislature or by an independent redistricitng commission, then a manageable standard might exist. That standard would be whether or not the procedure was followed.
I need to think about this a little more and perhaps get some feed back ideas from others with much more experience than I. But there is the nutshell of my idea.