Reagan did the amnesty with agreement that a wall would be built and immigration laws enforced. Then Congress refused to fund either. Never again. Once was enough. Self deportation and get in line for legal immigration with some credit if the illegal alien has no other criminal record and never took advantage of welfare/benefits here.
Once was too many.
At about the 14:50 mark here, the chief pollster explains how raiding businesses and holding employers accountable for hiring illegals is now 40 points more popular than Trump is:
https://www.youtube.com/watch?v=i4K5nNzuw6Q&t=332s
(The whole link is good, especially from where it starts.)