If a person said, "Vote for me, and I will build you a big, beautiful house that someone else will pay for. It won't cost you anything," I think that would be called bribery, which as far as I know is illegal.
Then after the person was elected, he said "You must build and pay for the house yourself, or there will be severe consequences," I think that would be called extortion, which is also illegal.
Now exchange "border wall" for "house," and "Donald Trump" for person.
