is there a metropolitan area as politically diverse as the Atlanta area? You can dry a compact 94% Obama district without trying, but you can also draw a compact 75% McCain district in the northern perimeter of the area.
Maybe Dallas or Houston.
I was thinking of drawing a Republican gerrymander to see how black I can make a district. Currently the blackest district in the US is only around 65% black (in Chicago). You could probably make an 85-95% black district in South Atlanta.
Also... I made this map a while ago to see how many majority-minority districts I could make. I only made minor changes when I got the election data, but if you unpack John Lewis & Hank Johnson's districts you might be able to shore up the 10th and 13th. You may also be able to make a hispanic majority district but I don't know if that would be ideal for a Democratic gerrymander.