What do you suggest, we can't shoot them - it will screw up the mid-terms.
Agreed, shooting them won’t work. Can’t build a wall in 13 days; probably can’t deploy much military in that time either. Probably most viable solution will be to get Mexico to act on our behalf. Close border, commerce, and remittances if the flow to the border does not stop. Let their military do the shooting so long as their guns are pointed south.