That's a lie, and one he's repeated often. Wishy-washy, hesitant support for a thing is not the same as being totally against a thing. His assertion that he was in opposition to it from the very beginning is a deliberate, egregious misrepresentation of his past views intended to convey authority on a subject that he simply does not possess.
I'll update the wording of my initial point to be more clear, since you have my original wording quoted here for posterity.
0. https://www.washingtonpost.com/news/the-fix/wp/2016/09/07/th...