The next wave moves to red states because of the draconian gun laws in their home states. Maybe not a huge number, but some, and that can make a difference.
Likewise, people living in Red States, like my kids are doing all they can to stay out of blue states, for the same reason - they’ll have to hand in their guns at the borders. So when good-looking jobs do pop up in those states, and it does happen, once in a while, they politely say “no, sorry”.
If people leave liberal States because of intolerable laws and political attitudes to more conservative States, doesn't that mean that the migrating conservatives are Republicanizing and conservatizing their receiving States?
The author cites demographers who assume that out-migration from 'Rat States carries the 'Rat Plague with it. I'd challenge that. I'd prefer to think that the migrants are conservatives who've been thoroughly inoculated by experience against the Deep Pink Plague. Case in point: Ayn Rand, who got a bellyful of Bolshevism before fleeing her native Russia.