A bit late seeing this. And I don’t think I have answers but a couple of thoughts on your questions.
I don’t think it’s coincidence but more like party affiliation have similar population sizes and similar voting participation rates then outcomes will likely be very close even when party platforms are far apart.
If the primary process pushes each side farther apart then any post primary move towards the center will only get shifts form those in the tail of the “other side” they want to steel votes from while probably alienating voters from a fatter section of the distribution they represent. So that is a p1*n1 = new votes taken from center and p2*n2 = votes lost from other half of your support distribution. I suspect p1 might be fairly high but n1 is very low while p2 is low (not sure how low to guess at) while n2 is probably much larger than n1. (This said, I do think you not only have generally seen that “move towards the center” in many elections as well as while in office. But seems to me this has not been happening in the more recent elections where are seeing party platforms much farther apart than say the past 40-50 years.)
A bit late seeing this. And I don’t think I have answers but a couple of thoughts on your questions.
I don’t think it’s coincidence but more like party affiliation have similar population sizes and similar voting participation rates then outcomes will likely be very close even when party platforms are far apart.
If the primary process pushes each side farther apart then any post primary move towards the center will only get shifts form those in the tail of the “other side” they want to steel votes from while probably alienating voters from a fatter section of the distribution they represent. So that is a p1*n1 = new votes taken from center and p2*n2 = votes lost from other half of your support distribution. I suspect p1 might be fairly high but n1 is very low while p2 is low (not sure how low to guess at) while n2 is probably much larger than n1. (This said, I do think you not only have generally seen that “move towards the center” in many elections as well as while in office. But seems to me this has not been happening in the more recent elections where are seeing party platforms much farther apart than say the past 40-50 years.)