I believe that the bottom line is, when he goes to enact these tariffs he will be told to stop by people smarter than him who understand these things better, or (if he ignores them) he will do it, it will fail and he will pull back somewhat.
I guess the third option is he does it, and it works, and everyone gets egg on their face. Somewhat unlikely, but so is him running, becoming popular, getting the nomination, being elected, surviving inauguration and becoming President.