Regarding voter purges, most of them are going to be simply because someone moved ~ maybe to a new district or out of state.
Republicans move more often than Democrats.
Simple fact of life.
Good chance the greater part of those changes are Republicans and not Democrats. But seriously, 700,000 or so is a drop in the bucket.
Well, no. The statistics are that FL, PA, and (I think) VA lost 80,000 Rs and 714,000 Ds. Three swing states alone were lost by only 500,000 votes. I've been through this before. You like to cite the 9m Dem advantage in 08, but over 2m (I think closer to 3) came from IL, CA, and NY. When you subtract those out, then another 714,000, then you're talking a much closer election without even changing a single vote.
But I challenge you to run the scenario #s I gave you.