And he will get Mexico to pay for it.
When Trump first offered the “get Mexico to pay for it” idea he was ridiculed. But it is actually easy to see how that could be done. Mexico needs to get into America much more desperately than we need to get into Mexico. This leverage is easily monetized and converted into funds for a wall. This sort of project is exactly what excise funds are for. Trump sees the big picture. People who see the big picture should be steering the ship.