Ben Smith reports. It sounds like it will be based on a challenge under section 2 of the Voting Rights Act.
The redistricting measures will have have to be precleared by the DOJ, because there are parts of Florida covered by VRA section 5. But assuming the measures get preclearance, I have a very hard time believing that the measures themselves violate section 2. (I’ll have to wait until I see the complaint and other papers to be sure.) It would seem much more likely to be able to launch an section 2 attack on a particular plan chosen through the process set forth in the measures.